In order to improve the quality of service（QoS） in service grid environment,the concept of Availability-Enhanced Job Execution Service（AJES） and its constructing method are proposed for the grid environment consisting of a large amount of low-availability resources.Then,an availability-enhanced model for job execution（AMJE） is derived from AJES,which redundantly schedules the resources to one or more grid sites within AJES,thus enhancing the availability required for job execution.In AMJE,different participants on behalf of their profits are described as a game,and a balance threshold of AJES availability is obtained.Experimental results show that AMJE increases the revenue of resource providers,improves the QoS level for end users,and exhibits good adaptability to dynamic grid environment.