一、解析非谓动词作主语

1. 不定式作主语。如：

To say is easier than to do.

解析：用不定式作主语时，常表示一次性的、具体的、特指的动作，并且用it作形式主语而将其后置。如上例可改为：It is easier to say than to do.

2. 动名词作主语。如：

Walking after supper is good for both young and old.

解析：若表示抽象的、习惯性的动作时常用动名词。

二、解析非谓语动词作表语

1. 不定式作表语。如：

What I can do is to give you some reasonable advice.

The library books are not allowed to be taken away.

解析：不定式作表语时，其后接动词（词组）主动式或被动式，与其最近的动词采用原形。

2. 动名词作表语。如：

His job is teaching.

The most famous writings in the world are worth reading.

解析：动名词作表语时，表语既具有动词特征又具有名词性，甚至有时表语和主语可以互换。如上例可改为：Teaching is his job.

3. 分词作表语。如：

The film is interesting, and my sister gets interested in it.

解析：现在分词作表语，表示主语所具有的特征，表语与主语之间是主动关系，并且常以物作主语，译为“某物怎么样”；过去分词作表语，表示主语所处的心理状态，主语和表语之间存在被动关系，并且常以人作主语，译为“某人感到怎么样”。具有这一用 法的有：surprise, interest, touch, move, puzzle, excite, tire, please, disappoint, satisfy, encourage等。