主动句是不是不用加be动词？

主动句含有be动词变成被动语态要根据be 动词在句子中的作用来定：
1、如果be 动词是系动词，后跟名词/形容词等作表语，那么这个句子没有被动语态， 因为没有宾语。
2、如果be 动词是助动词，没有意义，只是构成某种时态时，那么它的被动语态就根据句子时态用相应结构的被动语态。
如：
1). He is very happy . ( is 是系动词，这个句子没有被动语态）
2). He is doing his homework .(is 是助动词，实义动词是do，变被动语态）
His homework is being done by him .
3).. She was singing an English song last night . (was是助动词，实义动词是sing , 变被动语态度）
An English song was being sung by her last night .
4). He is writing a letter now .(is 是助动词，实义动词是write , 变被动语态）
A letter is being written by him now .
分析：

被动语态的结构是：助动词be +及物动词的过去分词。
常见的用法：
1)、一般现在时的被动语态结构：am / is /are +及物动词的过去分词
2)、一般过去时的被动语态结构：was /were +及物动词的过去分词
3)、一般将来时的被动语态结构：will +be +及物动词的过去分词
4)、含有情态动词的被动语态结构：情态动词+be+及物动词的过去分词
5)、现在进行时的被动语态结构： am/is / are +being +及物动词的过去分词
6)、过去进行时的被动语态结构：was / were +being +及物动词的过去分词
如：
(1). Chinese is taught at school.
(2). The river was cleaned last week.
(3). A new shop will be opened next week .
(4). The heavy box can be lifted by him.
(5). A story is being told by Uncle Li.
(6). The room w

加be的话，多是被动态。例如，The apple was eaten by Tom. 苹果被Tom吃了。而主动语态的单个动词一般不加be。例如，Tom ate the apple. Tom把苹果吃了。

另外，进行时在动词前面也有be。如，Sherry is singing. Sherry在唱歌。

另，在某些词组在动词前面会有be。如，be going to do, He is go...

主动句在实意动词做谓语时不用加be。 但在系表结构的情况下要加be。 例如：
He was tired / he is tired.
She is exhausted as it was a very busy day.

正常句式都不加be动词，主动句改被动句才加，被动句改主动句，不仅不加，还要去掉be动词。

主动语态直接使用动词进行变形就可以了，被动用be+动词过去分词。