The optimal load restoration model concerning cold load pickup is formulated as an optimization problem subjected to the system operation constraints including frequency， voltage and generation output， so that the maximum load may be picked up when maintaining reasonable frequency and voltage profiles. With IPLAN programming language provided by PSS/E， particle swarm optimization algorithm is applied to solve the proposed optimization problem. In addition， penalty function is introduced to handle system operation constraints. The proposed method is able to determine the load positions and amounts that can be picked up without disturbing system security and stability. Simulation is performed on a test system and the results demonstrate the effectiveness of the proposed method.