Abstract: In this paper,the phase pattern characteristics of the frequency diversity array(FDA)radar beam were studied.Since the frequency increment was introduced between the array elements,the FDA radar transmitting beam pattern showed two-dimension dependence on the angle and distance,the spatial beam direction changed with the distance,producing the phenomenon of bending,however,the phase pattern of the FDA radar did not show this characteristic.In this paper,two modeling methods,the phase distribution algorithm of FDA beam and Euler's formula,were proposed to establish the FDA beam phase distribution model firstly.Simulating and analyzing the two modeling methods,the Euler's formula was confirmed to be fit for studying the phase distribution of the FDA beam.Based on the optimal model,the phase distribution characteristics of the contour line,equiangular line and isometry line were simulated and analyzed,and thus,the in-phase wavefront of FDA beam were determined.The theoretical analysis and simulation results show that the phase distribution of the FDA beam does not produce the bending phenomenon compared with the phased array,and the distribution characteristic is basically the same as the phased array.