Abstract: The principle of the multi-frequency dithering algorithm is analyzed. The 2-11 channel coherent combining system is simulated as a mathematical model based on the principle of wave optics. The dynamic noise model is introduced, and the root-mean-square (RMS) phase error of the totally combined beam is taken as the evaluation function. The effects of noise frequency and amplitude on the phase locking effect of coherent combining system with different arrays are analyzed. When the noise frequency or amplitude is very large, the algorithm can no longer compensate the phase noise, the phase locking will fail. It is proved that there is an optimal interval between the gain coefficient and the modulation amplitude and only within this interval can phase locking be completed quickly. By introducing the concept of effective bandwidth control, the phase-locking performance of the multi-frequency algorithm has been evaluated intuitively. The research shows that the effective control bandwidth is directly proportional to the sampling frequency and the first-way modulation frequency, and inversely proportional to the noise amplitude, and the effective control bandwidth decreases with the increase of array size.