谓语受主语支配，须和主语在人称和数上保持一致，这叫做主谓一致。主谓一致一般遵循三条原则：语法一致原则，意义一致原则和就近一致原则。
1. 语法一致的原则
（1）以单数名词或代词，动词不定式短语作主语时，谓语动词要用单数；主语为复数时，谓语用复数，例如：
He goes to school early every morning.
The children are playing outside.
To work hard is necessary for a student.
（2）由and或both……and连接的并列成分作主语时，谓语动词用复数。例如：
Both he and I are right.
Mr Black and Mrs Black have a son called Tom.
但并列主语如果指的是同一人，同一事物或同一概念，谓语动词用单数。例如：
His teacher and friend is a beautiful girl.
The poet and writer has come.
（3）由and连接的并列单数主语之前如果分别由each, every修饰时，其谓语动词要用单数形式。例如：
In our country every boy and every girl has the right to receive education.
Each man and each woman is asked to help.
（4）主语是单数时，尽管后面跟有 but ,except, besides, with 等介词短语，谓语动词仍用单数。例如：
The teacher with his students is going to visit the museum.
Nobody but two boys was late for class.
Bread and butter is a daily food in the west.
（5） 一些只有复数形式的名词，如people, police, cattle, clothes等作主语时，谓语动词要用复数。例如：
A lot of people are dancing outside.
The police are looking for lost boy.
（6）由each, some, any, no, every 构成的复合代词作主语时，谓语动词都用单数。例如：
Is everybody ready?
Somebody is using the phone.
（7）有两部分构成的物体的名词，如glasses, shoes, trousers, chopsticks, scissors 等作主语时，谓语动词用复数。例如：
Where are my shoes? I can’t find them.
Your trousers are dirty. You’d better change them.
如果这类名词前用了a pair of等，则往往用作单数，谓语动词的单复数形式往往取决于pair的单复数形式。例如：
Here are some new pairs of shoes.
My new pair of socks is on the bed.
2. 意义一致的原则
（1）表时间、距离、价格、度量衡等的名词作主语时，谓语动词通常用单数。例如：
Twenty years is not a long time.
Ten dollars is too dear.
（2）有些集合名词，如family, team等作主语时，如作为一个整体看待，谓语动词用单数；如指其中每个成员，则用复数。例如：
My family is big one.
My family are watching TV.
（3）不定代词由all, most, more, some, any, none作主语时，也要依这些代词表示的意义来决定谓语动词的单复数形式。如果代词代表复数可数名词，谓语动词用复数；如果代词代表单数可数名词或不可数名词，谓语动词用单数。例如：
All of the work has been finished.
All of the people have gone.
（4）疑问代词作主语时，其谓语动词也有两种情况：主语表示复数意义，谓语动词用复数；主语表示单数意义，则谓语动词用单数。例如：
Who is your brother?
Who are League members?
（5）“分数或百分数+of+名词”构成的词组作主语时，其谓语动词要以of后面的名词而定。名词是复数，谓语动词用复数：名词是单数，谓语动词用单数。例如：
It is said that 35 per cent of the doctors are women.
Three -fourths of the surface of the earth is sea.
（6）half, the rest等表示不定数量的名词作主语时，如果所指为复数意义，动词用复数；如果所指为单数意义，动词用单数。例如：
I have read a large part of the book, the rest is more difficult.
Only ten students attended the class because all the rest were off sick.
（7）由what 引导地主于从句作主语时，通常谓语动词用单数形式。但如果所指内容为复数意义时，谓语动词用复数形式。例如：
What she said is correct.
What she left me are a few old books.
（8）凡是以“定冠词+形容词（或分词）”作主语，往往根据意义一致的原则决定谓语动词的单复数形式。如果这种主语指的是一类人，谓语动词用复数；如果指的是一个人或抽象概念，谓语动词用单数形式。例如：
The sick have been cured and the lost have been found.
The dead is a famous person.
3. 邻近一致的原则
（1）由连词or, either……or, neither……nor, not only…but also,等连接的并列主语，如果一个是单数，一个是复数，则谓语动词按就近一致原则，与最靠近它的主语一致。例如：
Either you or I am right.
Neither the children nor the teacher knows anything about it.
（2）在“There be” 句型中，谓语动词和靠近的主语一致。
There are two apples and one egg in it.
（3）as well as 和名词连用时，谓语动词和第一个名词相一致。
He as well as I is responsible for it.
不但是我，他对这件事也有责任。
（4）以here开头的句子，其谓语动词和靠近的主语一致。
Here is a letter and some books for you.