Abstract: To solve the problem of reducing the ghost generated by the source, while protecting the high-frequency component, expanding the bandwidth, this paper uses the over/under source combination theory to design multi-level air gun array. Based on the numerical simulation algorithm of the single gun, the cluster gun and the single sub-array, the theories of time-lapse excitation and the over/under source combination, we simulate the multi-level air gun array with time-lapse excitation, meanwhile, we develop the "Air-gun Array Design Software System." During the numerical simulation process, in order to avoid the resampling and other issues in time domain, we achieve the numerical simulation in the frequency domain to improve the accuracy. By comparing the simulation result with the actual data, we indicate the feasibility of the algorithm. Compared with the plane array, it shows that the multi-level air gun array of time-lapse excitation does exist superiority.