Cooperative business processes (CBP)-based service-oriented enterprise networks (SOEN) are emerging with the significant advances of enterprise integration and service-oriented architecture. The performance prediction and optimization for CBP-based SOEN is very complex. To meet these challenges, one of the key points is to try to reduce an abstract service’s waiting number of its physical services. This paper introduces a probability-based determination method (PBDM) of an abstract service’ waiting number, M _l , and time span, τ _i , for its physical services. The determination of M _i and τ _i is according to the physical services’ arriving rule and their overall performance’s distribution functions. In PBDM, the arriving probability of the physical services with the best overall performance value is a pre-defined reliability. PBDM has made use of the information of the physical services’ arriving rule and performance distribution functions thoroughly, which will improve the computational efficiency for the scheme design and performance optimization of the collaborative business processes in service-oriented computing environments.