Overloading assistant decision-making is one of the most important modules in integrated and coordinated defense system of large power system security and stability. When overloading occurs under current operating condition or post-fault operating condition, the adjustment amount of generators and discharge loads can be decreased by online computation of load transfer actions to get a more economical control strategy. Different limits are adopted for the calculation of overloading safety margin under current operating condition or post-fault operating condition. A comprehensive index for load transfer actions and active power actions is calculated. If load transfer action can not eliminate overloading, active power adjustment of generators and loads is required. Based on parallel computing technology, AC power flow calculation is performed for each control strategy to get the one with least cost and satisfying the precision requirements of active power adjustment.