所有从句的简化都是为了求精简，省略主语是为了避免与之前的重复，省略be动词是其本身无意义。副词从句的简化有五种不同的变化，我们分别讲解。
一、简化为Ving补语
如果副词从句是进行时，省略主语与be动词之后就是Ving形式，如果没有be动词和助动词，就得先改成进行式再省略be动词得到Ving形式：
① 连接词是否保留
副词从句的连接词有一定的词义功能，如while与before不同，虽然简化了，但有时候也不能省略，只有当句子的意思足够清楚的条件下才能够将连接词省略掉。
While lying on the couch, the boy fell asleep.
这一句中的while就可以省略，一般来说while（when）表示当……时，because、as、since表示因为，省略以后句子的意思依然完整，就可以省略。
② 没有be动词与助动词
Because we have nothing to do here, we might as well go home.
普通动词have，没有be动词可以省略，也没有助动词可以改写就只有先变成be+Ving形式，这里不是进行时态，而是词类的变化。
Having nothing to do here, we might as well go home.
注意：一般来说表示原因的连接词because、since等都需要省略，如果加上会十分累赘。
③ 应该保留的连接词
如果连接词省略以后句子意思不清楚，就不能省略
Although we have nothing to do here, we can't leave early.
简化成：
Although having nothing to do here, we can't leave early.
在这个句子中although表示一种转折，不能省略。
同理：
He raised his hand, as if he was trying to hit her.
简化成：
He raised his hand, as if trying to hit her.
as if 在这里表示好像，如果省略以后，读者可能默认为因为要打她，句子的意思就会改变。
④ being的运用
be动词一般在简化时都需要省略，但有时候也不能省略的过头了。
As I am a student, I can't afford to get married.
省略掉As I am以后，a student会被误认为是主语或者同位语，不适宜全部省略。可改写成：
As a student, I can't afford to get married.
Being a student, I can't afford to get married.
⑤ 连接词before、after、since作介系词
Before he was in school, he used to be a naughty child.
如果省略掉before he was就变成了：
In school， he used to be a naughty child.
没有了连接词before，就没有从前在学校的意思了，但是如果单纯的加上before in school，在语法上就有错误。before只能接名词类。为了将in school改成名词类，加入being即可：
Before being in school, he used to be a naughty child.
⑥ 时态问题
After he wrote the letter, he put it to mail.
简化成：
After writing the letter, he put it to mail.
需要保留连接词after，如果省略掉，就需要进行时态上的改变以保持句子原有的意思：
Having written the letter, he put it to mail.
⑦ 主语不同时
When the child was already sleeping soundly in bed, her mother came to kiss her goodnight.
从句的主语the child和主句的主语her mother是不同的，如果省略就变成了：
Already sleeping soundly in bed, her mother came to kiss her goodnight.
句子的意思表达不清楚，这时候就需要改变主语从句的结构，使得它与从句的主语一致：
Already sleeping soundly in bed, the child did not know it when her mother came to kiss her goodnight.
我们还可以保留两个不同的主语，改写成：
The child already sleeping soundly in bed, her mother came to kiss her goodnight.
注意事项：a、连接词要省略，这里省略when；b、后面必须配合分词补语（现在分词、过去分词）sleeping soundly，才能显示省略了be动词。
二、简化为Ven补语
副词从句如果原来是被动时态（be+Ven），简化之后没有了be动词，就变成了Ven。
① 是否保留连接词
Although he was shot in the knee, he killed three more enemy soldiers.
简化以后不能省略掉连接词although，因为although表达有“相反”的意思应该予以保留：
Although shot in the knee, he killed three more enemy soldires.
② before、after、since的特殊连接词
Before it was redecorated, the house was in bad shape.
简化为：
Before redecorated, the house was in bad shape.
副词从句省略以后before不能省略，不然表达的意思就是装修完成以后，和句子以前的意思不同。但是保留以后又会出现一个问题，就是before当介词使用，后面要跟名词类，我们加入being只是作为词类的变化：
Before being redecorated, the house was in bad shape.
③ 如何处理having been
Because they had been warned, they proceeded carefully.
如果保留had been就改写成：
Having been warned, they proceeded carefully.
如果省略掉hand been，就改写成：
Warned, they proceeded carefully.
having been如果后面跟的是过去分词，即使省略掉having been以后句子的意思仍然不变，也没有语法上的错误。就可以省略掉。
④ 主语不同时
如果副词从句与主句的主语不同，就得把主语保留下来
When the coffin had been interred, the minister said a few comforting words.
副词从句的 主语是the coffin，主句的主语是the minister，并不相同。简化时要同时保留：
The coffin interred, the minister said a few comforting words.
⑤ 助动词改写成to V形式
I'll only be too glad if I can help.
简化成：I'll only be too glad to help.
⑥ 动词只有be动词时
只有当副词从句的主语与主句的主语相同的时候才能将be动词省略。
1> 介系词短语
When you are under attack, you must take cover immediately.
简化为:
When under attack, you must take over immediately.
2> 形容词
While it is small in size, the company is very competitive.
副词从句的补语是形容词small，简化的方式相同
While small in size, the company is very competitive.
3> 名词
Although he was a doctor by training, Asimov became a writer.
简化方式相同：
Although a doctor by training , Asimov became a writer.
总结：副词从句的连接词通常有意义，需要保留，所有后面的简化没有太大的变化。只是一些特殊的连接词需要注意。
⑦ 改写成介系词短语
副词从句改写成介系词短语，是大幅度的简化。许多连接词都要找到接近的介词进行改写，只剩下一个名词空间来装下整个从句的内容。
when——on\upon；because——with；although——despite\in spite of；if——in case of；等
1> if改成in case of：
If there should be a fire, the sprinkler will be started.
In case of a fire, the sprinkler will be started.
2> although改写成despite
Although he opposed it, the plan was carried out.
Despite his opposition, the plan was carried out.
