Computational fluid dynamics (CFD) model has been widely applied in diesel engine research in the past decades. The integration of chemical kinetic model with CFD provides the opportunity for researchers to investigate the detail chemical reactions for better understanding of the combustion process of compression ignition engines. However, most of research using CFD has focused on the examination of temperature and species distributions within bulk gas. The detailed research to the chemical reactions is to some extent limited. This paper will present the development of a post-process tool and its application in evaluating the chemical reactions of a compression ignition engine simulated Converge CFD software coupled with chemical kinetics. The fuel chemistry used is a reduced primary reference fuel (PRF) mechanism validated against experimental data. The CFD model with chemical kinetics was validated against experimental data of a single cylinder diesel capable of representing the operation of a heavy-duty engine. The simulated heat release process and NOx emissions agreed well with experimental data. The post-process tool developed will be applied to examine the reaction rate of each reaction in each mesh cell. The reaction rate will be further processed to investigate the auto-ignition process of n-Heptane. The preliminary simulation work has identified the reaction paths of n-heptane during different combustion state. The contributions of the key radicals such as OH, HO2 and H to chemical reactions will be presented and discussed.