ajax post方式提交时需要在 data中添加 "csrfmiddlewaretoken":$("[name=csrfmiddlewaretoken]").val()

user/url.py

urlpatterns = [
    url(r"^check_username/$",views.check_username,name="check_username"),
    url(r"^check_password/$",views.check_password,name="check_password"),
    url(r"^check_password2/$",views.check_password2,name="check_password2"),
    url(r"^check_img_code/$",views.check_img_code,name="check_img_code"),
...]

user/register.html

{% load static from staticfiles %}
<script src="{% static "book/js/jquery-1.12.4.min.js" %}"></script>

<form action="{% url "user:register" %}" method="POST" id="register_form">
{% csrf_token %}
<table>
    <tr>
        <td>用户名:</td>
        <td><input type="text" id="username" name="username" placeholder="用户名位6-10位"></td>
        <td id="username_link"></td>
    </tr>
    <tr>
        <td>密码:</td>
        <td><input type="password" id="password" name="password" placeholder="密码位6-10位"></td>
        <td id="password_link"></td>
    </tr>
    <tr>
        <td>确认密码:</td>
        <td><input type="password" id="password2" name="password2" placeholder="密码位6-10位"></td>
        <td id="password2_link"></td>
    </tr>
    <tr>
        <td> 验证码:</td>
        <td><input type="text" id="img_code" name="img_code" placeholder="请输入验证码"></td>
        <td> <img src="{% url "user:create_img_code" %}" id="create_img_code"/></td>
        <td id="code_link"></td>
    </tr>
    <tr>
        <td><input type="submit" value="注册"></td>
    </tr>
</table>
</form>
<script>
var create_img_code = document.getElementById("create_img_code")

var url = "/user/create_img_code?num="
create_img_code.onclick = function () {
    var num = new Date().getTime()
    url += num
    create_img_code.src = url
}

$(function(){
    $("#username").blur(function(){
        $.ajax({
            "url":"{% url "user:check_username" %}",

            "data":{
                    "username":$(this).val().trim()
            },
            "success":function (data) {
                $("#username_link").html("")
                $("#username_link").append(data.r_link)
            }
        })
    })
    $("#password").blur(function(){
        $.ajax({
            "url":"{% url "user:check_password" %}",
            "type":"post",
            "data":{
                    "password":$(this).val().trim(),
                    "csrfmiddlewaretoken":$("[name=csrfmiddlewaretoken]").val()
            },
            "success":function (data) {
                $("#password_link").html("")
                $("#password_link").append(data.r_link)
            }
        })
    })
    $("#password2").blur(function(){
        $.ajax({
            "url":"{% url "user:check_password2" %}",
            "type":"post",
            "data":{
                    "password":$("#password").val().trim(),
                    "password2":$(this).val().trim(),
                "csrfmiddlewaretoken":$("[name=csrfmiddlewaretoken]").val()
            },
            "success":function (data) {
                $("#password2_link").html("")
                $("#password2_link").append(data.r_link)
            }
        })
    })
})
</script>

user/views.py

def check_username(request):
    username = request.GET.get("username")
    print(username)
    for i in User.objects.all():
        if i.username == username:
            r={"r_link":"该用户名已被使用"}
            return HttpResponse(json.dumps(r, ensure_ascii=False),
                            content_type="application/json;charset=utf-8")
    else:
        if len(username)>=6 and len(username)<=10:
            r = {"r_link": "ok"}
            return HttpResponse(json.dumps(r, ensure_ascii=False),
                        content_type="application/json;charset=utf-8")
        else:
            r = {"r_link": "用户名为6-10位"}
            return HttpResponse(json.dumps(r, ensure_ascii=False),
                            content_type="application/json;charset=utf-8")


def check_password(request):
    password = request.POST.get("password")
    if len(password)>=6 and len(password)<=10:
        r = {"r_link": "ok"}
    else:
        r = {"r_link": "密码为6-10位"}
    return HttpResponse(json.dumps(r, ensure_ascii=False),
                    content_type="application/json;charset=utf-8")

def check_password2(request):
    password = request.POST.get("password")
    password2 = request.POST.get("password2")
    print(password,password2)
    if password==password2:
        r = {"r_link": "ok"}
    else:
        r = {"r_link": "两次密码不一致"}

    return HttpResponse(json.dumps(r, ensure_ascii=False),
                        content_type="application/json;charset=utf-8")

def check_img_code(request):
    img_code1 = request.GET.get("img_code")
    img_code2= request.session.get("img_code")
    print(img_code1,img_code2)
    if img_code1==img_code2:
        r = {"r_link": "ok"}
    else:
        r = {"r_link": "验证码错误"}
    return HttpResponse(json.dumps(r, ensure_ascii=False),
                        content_type="application/json;charset=utf-8")