Abstract: In allusion to the redundant features and reliability guarantee requirements,this thesis tried to explore the effective ways for improving cloud service reliability．A trust redundancy reliability enhancement framework of cloud ser-vice was put forward based on the reliability architectue and management model．On the redundant design phase of the service being ready,based on the failure polling detection algorithm of voting protocol,a trust-aware fault-tolerant ser-vice selection algorithm was designed,and the calculation methods of min-number of fault-tolerant services were given．Based on the running fault-tolerant management framework of services combination,a cloud service invoking policy of ensuring service response time based on failure rules was presented．Experiments show that the fault-tolerant service selection algorithm and the cloud service invoking police have more practicality and effctiventness.

Key words: Cloud service,Reliability design,Trust redundancy,Failure rule