A syntactic and structural matching mechanism for service discovery was put forward, which tries to exploit the underlying semantics of web services to enhance the traditional syntactic service discovery. We commit WSDL (Web Service Description Language) as service description language. The syntactic matching mechanism is based on the textual similarity among WSDL documents using VSM (Vector Space Model). The structural information is extracted from WSDL document tree or the invocation sequence of a series of services which can be viewed as the problem of graph isomorphism. Then we combine the syntactic and structural similarity linearly to calculate the service similarity. Finally we provide a novel web services discovery framework named SG* to find the exact services meeting the users goals based on service similarity.