在宾语从句的众多引导词当中， that是一个使用频率最高，而又相当不起眼的词。对于其在宾语从句中的省略问题，英语的专家学者们的在著书立说中没能够全面地叙述，因而，它却往往被人们所忽视，也认为可有可无。那么它到底何时不可省略呢 ?本文就此问题作出更多的补充，并指出：这个词不可轻易省略，否则会产生语言的歧义。 Among the many introductory phrases of the object clause, that is one of the most frequently used but rather unnoticeable words. For its omission in the object clause, English experts and scholars can not fully describe in the book writing, therefore, it is often neglected by people and considered dispensable. So when it can not be omitted in the end? This article makes more supplements to this question, and points out: The word can not be easily omitted, otherwise it will produce language ambiguity.