In a load balancing cluster, the core of task distribution is the load balancing algorithm. Considering the deficiency in the load balancing algorithms adopted at present by the cluster servers,we know the servers may be skew. A new load balancing algorithm, which is based on the rough set theory and integrates the strong points of static and dynamic load balancing algorithms, is proposed in this paper. It avoids load imbalancing among servers, prevents the servers to be skew, and improves the performance of the server clustering system.