Trustworthiness plays an important role in service activities. However, it is not easy to define and compute the service trustworthiness as the evidence involves several information from different service party and maybe conflict at the same time. We discuss the definition and computation method of trustworthiness in this paper. The trustworthiness is acquired from service provider, service user, and service agent and then it is fused based on D-S evident theory. Finally, we testify that the trustworthiness can improve the precision of service discovery via simulation experiments.