Abstract: Firstly, the principle of phase interferometer direction finding algorithm is introduced briefly. Then the mathematical formula of 2D interferometer direction finding is deduced. A lot of limiting factors could affect the accuracy of 2D interferometer direction finding, which includes incident beam angle, length of short and long baseline,virtual baseline, signal noise ratio、position of array elements. The focus is on the correct probability of ambiguity-solving and the root-mean-square error. Based on the analysis of the Limiting factors, one design example of 2D interferometer direction finding technology is presented. According to the example, the result of MATLAB simulation proves the availability of the design. The root-mean-square error is less than 0. 9 degree.