In order to complete the clock synchronization planning of SDH network, this paper introduces a selection scheme of the accessed network elements of PRC based on iteration thought. Through setting the parameters in the synchronization network planning principles, according to the clock track distance from all the network elements to alternative network elements. In order to make the number of network elements covered within effective jump number as many as possible and make the average clock track distance of network elements covered as short as possible and make the PRC in the network as wellproportioned as possible. Iteration will make the results optimal. This scheme is encoded in MATLAB platform. This algorithm can intelligently plan out the network elements of PRC by automatic calculation instead of manual planning and reduce the difficulty of clock synchronization planning effectively. Meanwhile, it can improve the planning efficiency while ensuring the performance of the planning scheme.