The average scheduling strategy based on task numbers in fault-tolerant has shortcoming such as processing span and Quality of Service(QoS). Aiming at this problem,this paper proposes a grid scheduling algorithm based on priority,and then puts forward the design scheme of the hierarchical cluster system. The algorithm introduces the task in the process of task scheduling,task execution time remaining concept value density,cost budget and span,to make up for the task scheduling in the treatment of two span and QoS. Experimental results show that the algorithm has better effect in the completion rate,value realization rate,treatment rate compared with the original mechanism of scheduling strategy and Max-Min algorithm. The original mechanism is improved by using this algorithm. It can effectively improve the efficiency of system task execution,and the availability of system.