所有从属从句简化的原则都是一样的，即为求concise and clear out!状语从句中能省略的无非三个部分：主语、动词和连接词。1、主语重复时可以省略。2、动词分为三种：实意动词改成非谓语的形式;be动词因其意义是“空的”，可以省略;语气助动词改成to do的形式3、连接词是否省略关注的的是，省略连接词之后是否影响句子的意思。因为省略连接词是为了让句子简洁，但却万万不能损害句子的清楚性。
一般来说，表伴随的连接词(when/while)以及表原因的连接词(because/since/as等)，省略之后不妨碍句子的清楚性。因果关系本来就有非常强烈的暗示，如果保留下来会显得相当的刺眼、累赘。例子：While the boy was lying on the coach, he fell asleep.简化之后：Lying on the coach, the boy fell asleep.Because we have nothing to do here, we might as well go now.简化之后：Having nothing to do here, we might as well go now.Because we have been warned, we processed carefully.简化之后：Having been warned, we processed carefully. warned, we processed carefully.(having been与warned都有“已经”的意思，此处省略having been句子的意思也是完整的)
例子：Although we have nothing to do here, we can’t leave early.Although是为了让逻辑关系明确才保留，否则大家会认为是“因为无视可做，我们不能离开”反之，可以改成：Having nothing to do, we STILL can’t leave early.例子：He raised his hand, as if he was trying to beat her.As if省略之后，句子的逻辑意思也会改变。
Before/since/after既是连接词有是介词!例一：After he wrote the letter, he put it into the mail.直接省略连接词，句子会出现逻辑问题。可改写成：After writing the letter, he put it into the mail.Having written the letter, he put it into the mail.When he had written the letter, he put it into the mail.例二：Before it was decorated, the house was in a bad shape.改写成：Before being decorated/decoration, the house was in a bad shape.反例：After he shot in the knee, he couldn’t fight.简化之后，Shot in the knee, he couldn’t fight.
例子：When the boy was sleeping soundly in bed, his mom came in and kissed him goodnight.简化成：改法一：The boy sleeping soundly in bed, his mom came in and kissed him goodnight.改法二：Sleeping soundly in bed, the boy did not know it when his mom came in and kissed him goodnight.(sleeping soundly in bed是一个修饰语，但是却找不到归一，犹如悬挂在半空中漂浮不定)例子：悬挂修饰+having been的用法When the coffin had been interred, the minister said a few comforting words.
简化之后：The coffin (having been) interred, the minister said a few comforting words.