Aiming at the multi-channel power allocation problem of the communication system with a fix transmitting rate, which is undergoing intelligent jamming attack, an asymmetric Colonel Blotto game model was proposed. Under the condition of complete information, the equivalent optimal power allocation strategies at a single channel were deduced for the communication system and the jammer. Moreover, the only mixed Nash equilibrium strategy of them was proved, and the Nash equilibrium benefit was acquired. Based on the equivalent optimal power allocation strategies at a single channel, a direct column element exchange algorithm by multiple scanning was proposed to construct the multi-channel mixed power distribution matrix, which could adapt to more channels and wider power distribution range than the linear programming method. Through numerical simulation, the effectiveness of the multi-channel mixed power allocation matrix construction algorithm and the optimality of the proposed power allocation strategies were verified.