Coherent combining technology is an effect method to achieve huge amounts of fiber laser coherent combination, and phase-locking is the key.Two phase-locking methods, heterodyne detection and multi-dithering technique, for master oscillator power amplifier (MOPA) are compared, and a new phase-locking method is proposed based on multi-dithering phase-locked method. This method enlarges the number of optical beams and makes the experiment easier. Through simulation by Matlab solfware, we find that the root-mean-square (RMS) phase error of 64 beams combiniation is less than 0.08λ with the new method, while the RMS phase error of 30 beams combination is 0.15λ with the multi-dithering technique.