A premixed diesel fuel-air laminar flame system propagating in a duct between parallel plates is modelled using the energy and mass species conservation equations. The chemical kinetics of the diesel fuel-air combustion is simulated by an Arrhenius reaction rate expression with overall order of 1.5. The flame structure and heat release rate as well as the various parameters characterizing the flame behavior are obtained at the stantard condition of atmospheric temperature and pressure, and stoichiometric mixture. The effect of high initial temperature and pres-sure, and lean mixture strengh on diesel flame structure, heat release rate and characteristic parameters is comprehensively investigated.