Abstract: In software engineering,performance test is in general testing performed to determine how a system performs in terms of responsiveness and stability under a particular workload．The object of performance test is divided to two group.One is benchmark,and the other is non-benchmark．As performance test needs significant input of software resowrces, hardware resources and corresponding input of management and maintenance,traditional performance test takes a measure of miniature simulation．But this kind of miniature simulation causes inadequate test,and brings with serious consequences．Based on cloud computing,with its promise of on-demand,low-cost software and hardware resource,we builded the large scale performance test service platform to provide test service that is on-demand and customized.

Key words: Cloud computing,Test as a service,Performance test,Load test,QoS