进行时的构成是：主语+be动词+现在分词～.
（现在分词的构成详见第六章）
1) 现在进行时
I am watching TV now.
我正在看电视。
句型：主语+be（am，is，are）+现在分词～.
| 主语 | be 动词 | 现在分词 |
| 第一人称单数 I | am | V.+（动词）ing |
| 第三人称单数He, She,It | is | |
| 第二人称单数You | are | |
| 所有人称的复数You,We,They |
Look！Nancy is doing her homework
看！南希正在做作业。
They are cleaning their classroom.
他们正在打扫他们的教室。
2) 过去进行时
He was walking in the park at that time yesterday
昨天那个时候，他正在公园散步。
句型：主语+be（was，were）+现在分词～.
| 主语 | be 动词 | 现在分词 |
| 第一人称单数I | was | V.（动词）+ ing |
| 第三人称单数He,She,It | ||
| 第二人称单数You | were | |
| 所有人称的复数You , We , They |
I was watching TV then.
那时，我正在看电视。
When I came home， they were cooking in the kitchen.
当我进家时，他们正在厨房里做饭。