A reduced PRF mechanism was proposed for combustion simulations of PRE and diesel/gasoline fuels based on the latest LLNL mechanism. The reduced PRF mechanism consists of 73 species and 296 reactions. The major reaction pathways of the detailed mechanism were mostly retained in the reduced mechanism, which ensures its predictive capability, the ability to be extended to other fuels, and the high computational efficiency of the reduced mechanism. The important reaction pathways and reactions in the reduced mechanism are identified and discussed. Furthermore, the reaction rates of two reactions, HO2 + OH = HO2 + O-2 and HO2 + HO2 = H2O2 + O-2, in the hydrogen submechanism are discussed and updated. The reduced mechanism was validated with measured ignition delays, laminar flame speeds, premixed flame species concentrations, jet stirred reactor and shock tube species profiles, and PRF fuel HCCI and PPCI combustion and diesel/gasoline direct injection spray combustion data. The reduced mechanism predicts well the ignition timings, flame speeds, and important species concentrations under various validation conditions and shows reliable performance under different engine validation conditions. The overall results suggest that the current mechanism Can provide reliable predictions for PRF and diesel/gasoline combustion CFD simulations.