一般动词作为修饰，比如定语，会省略be。
eg：One of the treated dog was recovered. (其中有一只被治疗过的狗已经恢复了）
过去分词作后置定语时be 可省略。
eg：The boy called Tom is my friend .= The boy who is called Tom is my friend .
作并列谓语时后面动词的被动词语态中的be 常省略。
eg：The song is written and sung by the man over there . （was written and sung =was written and was sung 第二个was 省略了）这道歌是那边那个人写和唱的
注：Read，write, clean, wash, iron, burn, draw, cook, keep, cut, open, bolw, peel, sell, act等可以省略be动词
详解：这些词是由某些及物动词转化来的不及物动词，常和副词well, easily, smoothly等连用，且通常用主动结构表示被动含义。这些动词的主语一般是表物的词，且这些物往往具有某种内在的特点，这些句子的时态多用一般现在时或一般将来时，故可以省略be。