IT outsourcing has become a critical component of organizations, but improper expectations, ambiguous contracts and unclear goals frequently cause the failure of IT outsourcing. Especially we have to be concerned about the uncareful management of customer-supplier relationships based on a psychological contract perspective. This study focuses on the obligations of contractual parties for IT outsourcing which influence the outsourcing relationship(OR) and the successful performance of IT outsourcing(OP). The supplier obligations consist of the achievable infrastructure(S1) and capability(S2), and the customer obligations is composed of the acceptable environment(C1) and acceptability(C2) for IT outsourcing. This paper shows that the S1, S2, and C2 have an effect on the OR, the OR on the OP, and the S2 also on the OP directly. The four components of customer-supplier obligations are mutually related to each other. What is more, we must notice that the S2 has strong connections with the C2.