A new concept, Autonomous Web Service (AWS), to search requirement autonomously, is introduced in this paper. An intention-behavior-achievement mechanism based on environment ontology is proposed to specify the service request and the capability of AWS. A model of AWS aggregation driven by requirement has been figured out. The matching algorithm between the requirements and the AWS capability and the AWSs aggregating algorithm have been designed based on the intention-behavior-achievement mechanism. Finally, a case study is given to show the feasibility of this method.