The Design and Development of the on -line Black&White Game Abstract On-line games bring to a new form of entertainment. Until now, on-line games is charming more and more players. As the development of game industry, there will be more and more developers join in the game development team. The on -line Black&White game was developed by Microsoft Visual C++6.0 on Windows XP platform. In this game, two people can play the game on line, and the game also provides multimedia player function. The thesis start with introduction of network socket programming, the development processing of the on -line Black&White game are introduced in detail as followed. The thesis have a full touch on server and client socket programming, the communication between server and client was implemented, the algorithm of the five-in-a-row game, the multimedia playback functions. Key words: On-line games; Black&White game; VC; WinSocket; MCI