This paper numerically investigated the chemical kinetic process of a reacting n-dodecane spray flame under a compression ignition combustion condition. To achieve this target, a data processing method by coupling with the chemical kinetic mechanism was proposed and verified. The modeling results demonstrated that before ignition, the spray-flame structure was primarily composed of three regions: (1) an exothermic low-temperature heat release (LTHR) region in the upstream spray core, (2) an endothermic region surrounding the LTHR region, and (3) an exothermic high-temperature heat release (HTHR) region in the downstream spray. Based on the analyses of representative reactions and reaction pathways, the reaction R48 (C6H13 + O-2 = C6H13O2) was found to be the representative exothermic and endothermic reaction for both the LTHR and endothermic regions, while the reaction R276 (HCO + O-2 = CO + HO2) dominated the heat release in the HTHR region, which laid the foundation for the ignition. After the peak premixed heat release, hydrocarbons could not be fully oxidized due to O-2 deficiency and intruded into the high-temperature combustion region instead, leading to the diffusion combustion and initial soot formation. However, the upstream spray-flame structure was slightly affected by the further development of combustion, owing to the comparatively stable and lower temperature. The proposed code can provide more insights into the details of engine combustion and emission formation processes.