Abstract: The test and analysis of the surface pressure of the rail bar is of great significance in studying the internal response propagation law of the rail bar under the excitation of the explosion load in water. In this paper, the surface pressure of the rail bar under the action of a long-distance explosion load in shallow water was tested, and the explosive charge was 3kg B explosive. By fitting the empirical formula of the measured free-field explosion shock wave pressure peak in the water, and comparing and analyzing the peak pressure on the surface of the rail bar and the peak pressure in the free field in the water, the results show that the pressure peak value of the explosion surface in each surface of the rail bar far exceeds that of other walls. Under the same explosive and the same distance working conditions, the surface pressure of the rail strip is obviously greater than the peak pressure of the free field explosion shock wave in the water, and the main reason for this result is that the shock wave in the water produces complex reflection and diffraction on the surface of the rail strip structure. The test and analysis of the surface pressure of the rail bar have a certain reference for the test and damage analysis of the surface pressure of obstacles in the water under the explosion load.