To realize the optimal allocation and target controllability of automatic generation control (AGC) regulation capacity, an AGC allocation method based on genetic algorithm(GA) is proposed. Firstly, the basic principle of AGC is analyzed, and the mathematical model of unit allocation to find the optimal solution under constraints is provided. Then, GA is tentatively applied to the allocation of a AGC unit, and the crossover and mutation are performed according to the capacity segment and state segment respectively. Combined with the priority method, the continuous variables in the model are processed to improve the convergence performance of AGC. The example of the actual system shows that our method can overcome the disadvantage that the integer programming method may not acquire the optimal solution, and achieve a certain economy, which also provides a new and effective strategy for the allocation of AGC units.