Abstract: Permission of multiple users making concurrent design in a region of the same pattern over the Internet is the basic requirement of a collaborative pattern design system. As the conflict led by several designers on different sites is unavoidable, it becomes one of the key issues in a collaborative design system. In this paper, we present the definition of conflict, describe some methods to prevent conflict, and propose an efficient algorithm for detecting conflict. The solution to the problem of conflict based on locking conflict operations is a novel way that can protect users' intention in collaborative design even if conflict occurs. By using these methods and algorithms, the problem of conflict brought in collaborative design in the distributed environment is well solved.