For there is no overload control signal between Service Switch Point and Service Control Point at CALEL 2 stage of mobile intelligent network, we provide an overload control algorithm realized in SCP. In the algorithm, we use a leaky bucket controller in access module to filter user calls and set an appropriate finite buffer in SCF module for protection further. The results of analysis and simulation indicate that by making the call arrival rate to SCF module equal its service rate when SCP become overloaded, the call processing rate of SCP system can keep its optimal value.