In order to study the effect of water content on the performance of porous granular ammonium nitrate on-site mixed ammonium amine explosives, five groups of on-site mixed ammonium amine explosives with different water contents were prepared by controlling the water content in the aqueous phase. We used scanning electron microscope to observe the internal microstructure of porous granular ammonium nitrate, and Brinkley-Wilson method to carry out theoretical calculations on the heat of detonation and detonation velocity of the explosives. The solubility of porous granular ammonium nitrate at different water contents was tested, and the viscosity of the ammonium amine explosive matrix, the immersion conductivity and the detonation velocity were tested. The results show that with the increase of water mass fraction from 9% to 17%, the mixing homogeneity of ammonium amine explosive matrix increased, the initial viscosity decreases from 218539 mPa·s to 99443 mPa·s; the conductivity of the explosive immersed in water with different water content for 3 h first decreased from 1.416 mS/cm to 1.234 mS/cm, and then increases to 2.600 mS/cm; the theoretical detonation velocity decreases from 4943 m/s to 4716 m/s; the actual detonation velocity is affected by the content of solid ammonium nitrate, first increasing from 3376 m/s to 3676 m/s, and then decreasing to 3631 m/s. In actual production, the mass fraction of water in on-site mixed ammonium amine explosives should be controlled at approximately 13%. At this water content, the explosives exhibit optimal water resistance, and achieve a relatively high actual detonation velocity.