The effect of atmosphere turbulence on phase modulation signal in coherent beam combination with multi-dithering technique is studied. Analytical formulas for the phase modulation signal of beam array propagating in a turbulent atmosphere are derived based on extended Huygens-Fresnel integral. Then the effects of propagation distance, turbulence intensity, filling factor and size of beam array on phase modulation signal are numerically calculated. The results show that with transmission distance increasing, there occurs a maximum of the amplitude of phase modulation signals. With the intensity of atmosphere turbulence increasing, the maximum of amplitude of phase modulation signals will appear in a shorter distance. When fill factor does not change, the distance between the laser source and the maximum of amplitude of phase modulation signals will be increased with of the dimension of laser beam increasing. When the dimension of laser beam does not change, the distance between the laser source and the maximum of amplitude of phase modulation signals will be increased with fill factor decreasing. Finally, the effects of parallel beam array and conformal focused beam array on phase modulation signal are compared, finding that the distance between the laser source and the maximum of amplitude of phase modulation signals can be changed by changing the focusing distance of conformal focused beam array.