A novel job scheduling algorithm based on credit model was presented for cluster system. In the credit model, every computing node was looked as a c redit entity. The scheduling system gave each entity a credit value according it s power ability, its status and its history records. The scheduling system also gave a credit estimate to the entire cluster, and according this estimate and en tering job request decided to reject or accept the job. It was realized based on OpenPBS framework. It was also simulated using GridSim toolkits to proceed a co ntrastive test with FIFO(first input first output) and Libra. The result shows that it works well.