Research on cavitation is very significant for preventing cavitation erosion and for making use of bubbles effectively. Characteristics of cavitation in canonical ensemble are studied by molecular dynamics simulation. Effects of temperature and numerical density on cavitation are analyzed. Comparison with lattice Boltzmann method is also conducted. Simulation results indicate that the temperature and numerical density may affect cavitation remarkably. The formation of cavitation bubbles becomes unstable as the temperature increases, and even hard to occur. A lower numerical density makes cavitation bubble form easier. Moreover, as numerical density reduces, the temperature effect on cavitation becomes less.