As an important technology of reducing NOx emission,the method of exhaust gas recirculation(EGR)has been widely used in modern diesel engines. As a result,the fresh charge in cylinder contains high concentration CO2and steam. To analyze the influence of these factors on evaporation and combustion of diesel fuel,the non-equilibrium evaporation model was used to calculate the droplet's evaporation and combustion process of n-heptane in air with high CO2and steam. The effects of ambient parameters,droplet initial parameters,CO2/steam mass fraction on the ignition delay time,droplet lifetime and flame structure parameter were investigated. Results show that the ignition delay time and lifetime are significantly short with the increase of ambient temperature and pressure. Compared with the influence of ambient pressure on the evaporation and combustion,the effect of ambient temperature becomes even more pronounced. Raising the initial droplet temperature can shorten the ignition delay time and droplet lifetime,and increase the ratio of flame radius to droplet radius. Since the droplet mass gains and droplet specific area decreases with the increase of the droplet radius,the droplet's ignition delay time and lifetime become longer. In case of unchanged oxygen mass fraction of ambient gas mixtures,only adding CO2/steam mass fraction has little effect on the evaporation and combustion of n-heptane droplet.