Abstract: Materials may melt and even vaporize under hypervelocity impact. In order to consider the material phase changes under hypervelocity impact, GRAY three-phase equation of state and Tillotson equation of state were applied in this paper, and hypervelocity impact numerical simulation was carried out by using the two equations of state, respectively. The simulation results show that when the impact velocity is under 3 km/s, there are no obvious differences between the debris clouds characteristic parameters except the diameter of penetration holes given by the two equations of state; but when the impact velocity exceeds 3 km/s, there are notable differences between the debris clouds characteristic parameters given by the two equations of state. The results show that the material phase changes under hypervelocity impact have significant influence on the debris clouds characteristic parameters.