Abstract: The estimation and management of the response time is an important problem of spatial information service.Aiming at the automatic generation of spatial information service chains,the determinate model and the probability model for response time estimation is established,and the concepts of critical path,critical service and service slack are defined.In order to ensure the response time of services chains satisfy the requirement of users,an optimal service composition algorithm based on critical path method is proposed to select appropriate component services.Experimental results show that this algorithm optimizes the response time of spatial information service chains.