In this paper, the sensors were laid around explosion center to obtain shockwave travel time, then traveltime tomography methods were used to reconstruct overpressure field of underwater explosion induced shock wave. Due to insufficient sensors, the reconstruction is rather difficult. This problem of incomplete data needs more stronger algorithm to execute. The paper lists four common algorithms to solve the problems, they are ART algorithm, SIRT algorithm, SART algorithm and EM algorithm. Though the results of the appraisals, the EM algorithm with higher accuracy and velocity is feasible in actual test, and can help to save the costs.