In this study, an in-house multi-dimensional code has been developed which simulates the combustion of n-heptane in a Homogeneous Charge Compression Ignition (HCCI) engine. It couples the flow field computations with detailed chemical kinetic scheme which involves the multi-reactions equations. A chemical kinetic scheme solver has been developed and coupled for solving the chemical reactions and calculation of heat release. The effect of parameters such as, initial temperature, initial pressure, compression ratio and equivalence ratio on the combustion characteristics of a n-heptane fuelled HCCI engine have been studied. The chemical kinetic scheme used here, consists of 27 elementary reactions and 26 species which involves the reactions required for calculation of NOX also. The results show good agreement with available experimental data.