Abstract:Refactoring is a common way of improving software maintainability and software quality in modern software development and maintenance. In daily revision, refactoring patterns usually mix with code changes accomplishing other tasks such as bug fixing and feature addition, which makes the change understanding very complicated. It facilitates changes understanding to identify refactoring patterns that can isolate refactoring from other types of code changes. As far as I am concerned, there is no method and tool which have been proposed to identify code refactoring by code change types and similarity comparison. We proposed An identifying algorithm for refactoring patterns, based on fine-grained changes type and text similarity. The algorithm is used for refactoring patterns of extract class. The algorithm has been tested on 4 open source projects, with an average 82.6% accuracy.