The approximate DF value based on equivalent array with one-dimensional single baseline has the disadvantage that account accuracy is lower. The analysis shows that the deviation behavior displayed by two adjacent equivalent arrays with single baseline is even opposite. And then, making use of mutual counteraction method, the result that the deviation of DF is going to zero can be obtained by taking arithmetical average for two DF value. The new method keeps the feature that approximate solution of DF has preferably measurement precision and helps to improve the engineering design performance of phase difference DF technique.