语的被动语态中，不管什么时候都必须要用be动词，一般现在时被动语态be要根据人称变成am， is 或者are。过去时be要变成was 或者were。现在完成时be要变成have或has been。
英语被动句什么时候加be
被动语态的构成是be+过去分词，其中be要根据具体的时态变化。
如果用于现在完成时和过去完成时，be要变成have/had been，再加被动语态
如果be在情态动词后面，可以保持be的原形
This can be predicted. 这是可以预见到的。
All the problems have been solved. 所有的问题都解决了。
一般地讲，被动语态可用于英语的各种时态。为了能准确地运用被动语态，重点是要掌握be动词的各种时态变化。各种时态的被动语态举例如下：
1、 一般现在时的被动语态. am / is / are + 动词的过去分词
Our classroom is cleaned every day.
This car is made in China.
2、一般过去式的被动语态: was / were + 动词的过去分词
His desk was cleaned just now.
The station was built in 1928.
3、现在进行时的被动语态: am / is / are + being + 动词的过去分词
A new factory is being built in our city now.
Some trees are being cut down in the park.
4、过去进行时的被动语态: was / were + being + 动词的过去分词
A new factory was being built in our city at that time.
Some babies were being looked after by Miss Chen last year.
5、一般将来时的被动语态:
(A) will / shall + be + 动词的过去分词
(B) am / is / are + going to be +动词的过去分词.
Some new factories will be built in our city this year.
Your watch is going to be mended in an hour.
6、过去将来时的被动语态: (1).would / should + be + 动词的过去分词 (2).was / were +going to be + 动词的过去分词.
She said that some new factories would be built soon in our city.
He thought that your watch was going to be mended after an hour.
7、现在完成时的被动语态:have / has + been + 动词的过去分词
Some new factories have been built in the city since last year.
Your watch has been mended already.
8、过去完成时的被动语态:had + been + 动词的过去分词
He said that some new factories had been built in the city.
I didn’t know that my watch had been mended .
9、含情态动词的被动式：can/may/must + be + done
例如：He can not be found. / I must be paid for this.
