独立主格结构是由名词或代词加上其他成分(分词、不定式、名词、代词、形容词、副词或介词短语)构成。
在语法上是一个独立的短语，不是句子，在意思上依附于整个句子，具有以下特点：
1、独立主格结构的作用相当于状语从句。可表示时间、原因、条件、行为或者伴随情况。
2、独立主格结构可置于句首，也可以放在句尾。
3、独立主格主要用于书面语。4独立主格结构的逻辑主语与语法主语不同，不能指同一个人或者同一事物。
若名词/代词与非谓语构成主动关系，用doing或having done;若名词/代词与非谓语构成被动关系，用done或having been done。having done与having been done 强调非谓语发生在主句谓语之前。
结构
1. 名词/代词+分词(包括现在分词和过去分词)：
The boy ran quickly,his father following. (表示伴随情况)
He lay on his back,his hands crossed under his head.(表示伴随情况)
2.名词/代词+形容词：
They started home,their minds full of plans for increasing production.(表示伴随情况)
He was silent for a moment,his lips tight.(表示伴随情况)
3.名词/代词+副词：
He put on his socks,wrong side out.(表示补充说明)
The war over,all the Chinese people’s volunteers came back to China.(表示补充说明)
4.名词/代词+介词(短语)
She came in,a baby in her arms.(表示伴随情况)
He went off,gun in hand.(表示伴随情况)
主要用法
1.表示时间：
His homework done, Jim decided to go and see the play.
=After his homework was done, he decided to go and see the play.
2.表示原因：
The last bus having gone, we had to walk home.
=Because the last bus having gone, we had to walk home.
3.表示条件：
Weather permitting, we’ll go for an outing tomorrow.
=If weather permitting, we’ll go for an outing tomorrow.
4.表示伴随情况或伴随状况：
They walked through the forest,an old hunter leading the way.
5.表示补充说明：
He lived in a wooden house with two rooms,one being a bedroom and the other being an office.
=He lived in a wooden house with two rooms, one was a bedroom, the other was an office.
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