In order to overcome the difficulties of the large aperture laser system, combining the output energy of multiple laser beams with small aperture at the target surface was a feasible scheme. To meet the target surface requirements for the uniformity and symmetry of the irradiation, the synchronous control precision of multi-pulse was analyzed in detail. The results show that multi-pulse irradiation affects the synchronization of the energy distribution center in far-field directly. While one single beam pulse delay is greater than or equal to 2 times of the pulse width, the peak value of the light intensity on the target surface will fall down to 75%. If the control errors of two pulses are occurred with the same degree peak value of light intensity will fall down to 50%. Otherwise, when the control error of the pulse width is twice as large as the ideal pulse width, the peak value of the intensity on the target surface will drop to 87.5%.