Abstract: The jet formation of a heavy gas cylinder under planar shock wave impact is a very interesting phenomenon which is closely associated with the gas properties and the shock wave strength. It is worthwhile to investigate the complex wave structure in this process due to its academic value. The R₂₂ cylinder jet formation process under planar shock wave impact is simulated using Level Set method to capture the gaseous interface, and rGFM to define the interfacial boundary conditions. The development of wave structure is elucidated, typical wave patterns that lead to the jet formation is highlighted, and the reason of the jet formation is expounded from a perspective of wave pattern. Cases with different shock strengths are presented in this study. It is found that the shock strength plays an important role in determining the formation of jet and even the characteristics of the jet structure if the jet is formed. A critical shock strength is concluded beyond which the jet cannot be formed. It is expected that the presented results could guide and verify the experimental results.