Similar to explosive blasting, the destructive effects of carbon dioxide phase change blasting include two continuous processes: stress wave stage and pneumatic stage. Nevertheless, the contribution of gas penetration to cracking range in CO2 phase change blasting remains a pending question. It is unwise to ignore the effect of gas penetration in numerical simulations. To this end, this paper developed a finite-discrete element program for rock blasting that can consider gas penetration. Then, the CO2 isentropic P-V relationship obtained based on the Span-Wagner state equation was introduced into the numerical simulation program, and the CO2 phase change blasting numerical simulation under two different situations was carried out: Case 1, the function of gas penetration is ignored; Case 2, the function of the gas penetration is considered. The numerical simulation results show that the pneumatic penetration contributes 74% to the fracturing range and contributes 72% to the cumulative crack length, which indicates that gas penetration plays a major role compared to stress wave.