They say that process of thought and of expression are necessary for writing. But in reality, we fail to teach the process of thinking. In this paper "analogy" will be studied among various principles of thought. This paper will chase backward and construct the process of thinking from a completed composition. The subjects of this study are Chang Yu`s , and . It is interesting to find that these works are made up of same "analogy" logic, but they show different aspects. This different aspect of analogy can be "a principle of thinking" and be used practically. is `the extension of similar structure` type. This regards brush and man in the same light, and extend the structure of brush to the structure of man`s world. This type conducts a new conclusion from the similarity of two subjects. is `the circulation structure` type. This pursues the man`s moral nature in view of the case of bamboo. This type is same at `the extension of similar structure` type in having a base of similarity of two subjects, but it is different because it finds a needed nature from the original source. This type is a form of abstraction of a needed condition or an essential element for the sake of the alikeness. is `the duplex structure` type. In this type, analogy is developed twice. At first, crooked trees and men are regarded in the same light. Then the focus moves to the difference between two subjects. Finally, on the basis of the difference between trees and men, it is concluded that men`s world is much more wrong and crooked. This type is developed in similarity first. Secondarily, it conducts a new view on the basis of difference. According to the types of analogy, the mechanism of analogy is divided into three patterns. In the `the extension of similar structure` type, the mechanism is "relating". In the `the circulation structure` type, the mechanism is "making up for". In the `the duplex structure`, the mechanism is "discriminating." As a result, it seems the study on the type and mechanism of analogy is significant in creative writing. Analogical inference can be used as the method for not only to get a new view on knowledge, but also to express them.