As the number of Web services has increased, how to locate services becomes an important research issue. Previous works for semantic Web services discovery have been proposed. Since they lack a sophisticated scheme of specifying services' advertisements and users' requirements, they may not discover services, which satisfy the intention of service requesters. To resolve this problem, we propose a noble scheme to represent and utilize the dependency between I/O parameters. In addition to the conventional semantic matchmaking of I/O parameters, the dependency relations among them are also considered. From experimental results we can find that the proposed method based on the parametric dependency relations performs better than previous works.