The classical Chinese grammar has complexity that we can't exactly distinguish like that of English, because it has many adaptabilities in using words and expressing sentences. This paper is a study on the adaptable styles presented in the grammar of classical Chinese. The meaning of adaptability in grammar means that Chinese people receive two or more methods of expression from the usage of words to the structure of sentences. Every Chinese word has many different meanings, so the adaptability of expression begins from using words. Every Chinese word can also be changed into the other part of speech in a sentence. In addition to that, the adaptability of expression shows so many kinds of methods in the structures of sentences. The writter often uses duplicate methods in making sentences by changing the order of words, and omits some words that should be written when he thinks readers can understand them. The methods which do not use the tense, the singular and plural number in every sentence are dependant on readers' estimation. There are original and basic patterns of Chinese sentences, but writers sometimes do not use them but the other patterns even to write a same meaning sentence. For example, there are patterns of interrogative subjunctive and conditional sentences, but writers often do not use them but use the other patterns when they write. This comes from adaptability of expression in classical Chinese, therefore readers have to carefully read all of sentences. The adaptability of expression is very convenient for writing, but in the other hand, it has many complexities. For many different results come from it. This paper has analyzed different and complicated parts of Chinese grammars come from the adaptability of expression.