In the study of the steady response of the stiffened plate under the underwater explosion, the previous researches mainly use the transient explicit algorithm, and the results of the steady responses have some precision defects. An improved numerical simulation method of underwater explosion is proposed. This method uses ABAQUS / Explicit Standard algorithm to establish a joint numerical simulation method for the transient explicit and steady implicit static analysis. This method is used to analyze the "transient steady state" response of a stiffened plate frame. The results show that the difference between the simulation results of the combined "transient explicitsteady implicit" algorithm and the test results is less than 10%, which shows that the method can be used for the response analysis of stiffened plate structure under underwater explosion, and the results of the combined "explicitimplicit" algorithm are closer to the test values, with an error reduction of 39.8%.