Learn the baseline definition of the IEEE, baseline is closely linked with the modification control, but the software change also involves the version change. After identifying all software configuration items and carrying out the version management, ensure that the software configuration items are real under control in the complex development process, and in any case can be able to rapidly restore a historic state. The version control purpose is to easily distinguish the version changes, retrieval and tracking, to indicate the relationship between the various versions. With the increasing complexity of software systems, as well as the user needs, software updates frequently, version control gradually becomes an important control process of software configuration management, is the important contents of the quality management in software engineering.