The performance problem of BGP has raised great concerns both in industry and research. With rapid expansion of Internet, how to improve the performance of BGP to support more BGP neighbors in a high-speed router is a practical urgent problem. In this paper, the authors presented a Minimal Cores Computing (MCC) algorithm based on multiroot tree model to compute the minimal cores for parallel BGP in the context of the multi-cores platform. The algorithm is an approximation algorithm as the problem is a nonlinear programming problem. Simulation results show that MCC can get reasonable good speedup with minimal number of cores. MCC can give direction to the design of the control node in a core router.