Abstract: The wetting and spreading behavior of molten AgCuTi on the surface of TiNi alloy was investigated using the molecular dynamics simulation method. The wetting behavior of AgCuTi brazing alloy on the surface of single-crystal and polycrystalline TiNi alloys at different temperatures of 1073, 1123, 1173 K, and 1223 K was investigated. By analyzing the density distribution and simulating the wetting and spreading image in the equilibrium state, it was found that the increase in temperature had a significant promotion on the wetting process. No obvious dissolution reaction was observed during the wetting process. Instead, a precursor film dominated by Ag was formed. As the temperature increased, a small amount of Cu and Ti diffused into the TiNi matrix in the melted AgCuTi, and a small amount of Ti in the matrix diffused into the brazing alloy. By analyzing the mean square displacement, it was found that the formation area of the precursor film increased correspondingly with the increase in temperature. The wetting and spreading of droplets exhibited isotropy, forming a regular circular spreading area. By analyzing the wetting properties of molten AgCuTi on single-crystal and polycrystalline substrates, it was found that the presence of grain boundaries significantly promoted wetting properties.