First, the principle of matched-phase of signal of three sensor array is introduced, and the formulae of extracted signal are derived. Then, the performance of principle of matched-phase of signal in coherent interference suppression is analyzed. The effect caused by fluctuation of interference spectrum amplitude on the principle of matched-phase of signal is studied, and the formulae of relative error of extracted desired signal are derived when interference spectrum amplitudes are fluctuant. Again, the viewpoint is presented that the addictive noise can be viewed as the fluctuation of interference spectrum amplitude. Finally, based on the fact that the number of practical array elements is commonly more than three, two methods, three sub-arrays and least square method, are proposed to improve the performance of principle of matched-phase of signal by exploiting redundant elements of array. Simulation result shows that the performance of three sub-arrays and least square method is much better than that of the three sensor array. Also, a conclusion is given that the computation load of three sub-arrays is less than that of the least square method, but the three sub-array method is applicable to the uniform line array and the least square method is suited to arbitrary array.