In order to overcome the three detection methods defect of density bottle density detection method, hydrostatic weighing density detection method and standard measuring density detection method, design a sealing detection device for testing the shaped gunpowder grain density. Using inert gases such as nitrogen or helium as an intermediary, permeated into the sample in the tiny voids and surface of the irregular air trapping, fast and accurate determination of test piece volume to achieve an accurate determination of explosive forming density, analyze composition and function of the device, give the technological process and technical parameters. The results show that the method has high sensitivity and convenient operation, it can realize the automatic revision of original value, improve work efficiency greatly.