Propylene is used for manufacturing commonly used raw materials and synthetic materials for petrochemical processes. However, it is a volatile and flammable material that poses fire and explosion risks. Nitrogen is inexpensive and can lower the propylene explosion limit because of the dilution effect when used as an inert gas. This study measures the explosion limit, minimum oxygen concentration (MOC), explosion pressure, explosion pressure rise rate, and deflagration index (Kg) values for propylene and nitrogen at 25 °C. Results showed that the lower explosion limit of the explosion range did not significantly change with an increase in pressure from 0.10MPa to 0.25MPa; however, the upper explosion limit increased significantly. Furthermore, the MOC decreased as pressure increased at 25 °C, while both the maximum explosion pressure and maximum explosion pressure rise rate increased, thereby increasing the explosion risk. The risk of propylene was predicted by the Kg values determined using the maximum explosion pressure rise rate and volume based on the experimental data. Therefore, through this study, we provide basic data on safety references for preventing fire and explosion accidents.