Abstract: Software comprehension is an important step of software maintenance, and it is regarded as an increasing pattern matching process from one level to another. First, in this paper, the state of the art and development directions of basic factors of software comprehension are systematically studied, i.e., concepts and models are compared, tasks and strategies are analyzed, objects are discussed, environments and tools are classified,and all kinds of software comprehension methods are analyzed. Then, the progress made in object oriented software comprehension is also discussed. Finally, some good conclusions are given, and future work is also presented.