The effects of heating time, jet height, jet pressure and high-temperature antioxidant coating on high-pressure jet descaling of 40CrNi4Mo1V gun steel were investigated. The research results show that the descaling width decreases with the decreasing of jet height, the jet height is reduced from 130 mm to 110 mm, the descaling width is reduced by about 11 mm, and the effect of jet pressure on the descaling width is not significant. When the jet height is reduced to 110 mm, the overlapping region of neighboring jets basically disappears. With the increasing of jet pressure and the decreasing of jet height can increase the jet striking force. Under the experimental conditions, the jet pressure exceeds 30 MPa resulting in the effective removal of iron oxide scales from the specimen surface. The 40CrNi4Mo1V gun steel forms iron oxide scales at high temperatures, in which the (Fe, Cr) oxide phase and the (Fe, Ni, Mo) alloy phase are intertwined. The adhesion between iron oxide scales and substrate is notably strong, which complicates the removal of iron oxide scales from the substrate, resulting in the formation of a substantial number of FexOy-CrxOy endogenous oxidized particles. For the specimen coated with a high-temperature anti-oxidation coating, an extremely thin FexOy layer with the thickness of less than 10 μm is formed on the surface after descaling. There are extremely small amounts of endogenous oxidation particles inside the matrix, and the depth of these particles does not exceed 40 μm.