In recent years, n-pentanol has attracted much attention because it can reduce the dependence on fossil fuels and the pollution emissions of engines. As important components of diesel, aromatic hydrocarbons play a significant role in soot generation. In this work, a new reduced chemical kinetic mechanism of n-heptane n-butylbenzene n-pentanol polycyclic aromatic hydrocarbon (PAH) was established, containing 178 species and 746 reactions for diesel engine applications. On the basis of the reduced mechanism of n-heptane PAH, the proposed mechanism was developed by adding the reduced mechanisms of n-butylbenzene and n-pentanol. Direct relation graph with error propagation (DRGEP), sensitivity analysis, and rate of production (ROP) methods were employed to reduce the detailed mechanisms of n-butylbenzene and n-pentanol, respectively; then, the sensitivity analysis method was employed to optimize the simplified model. In order to verify the reliability of the current mechanism, it was used to extensively verify experimental values with ignition delays, laminar flame speeds, and species concentration profiles and direct injection compression ignition (DICI) engine emission and combustion data. The simulation results show that the experimental values are in excellent consistence with the predicted combustion characteristics and soot, NOx, and CO emissions, indicating that the current mechanism is able to be used for the diesel engine simulations. Lower emissions of soot and NOx were obtained with n-pentanol/diesel blends compared with pure diesel, mainly owing to the longer ignition delay, which results in sufficient mixing combustion.