Most existing trust management systems have two main problems

(1) hard to provide security guarantee for web resources since their implements do not comply with Web Service standards;(2) the chief trust engine runs at a low efficiency

cannot fulfill demands of on time security policy in the all long changeable environment.We use java language to design and implement a trust engine oriented to Web Service based on mobile agent to satisfy security demands in the open and dynamic web environment.The main work of trust engine is to verify whether a web resource can be visited by some client.We use mobile agent to do bidirectional trust chain discovery to impro ve the efficiency of the trust engine.