In order to explore the mechanism of liquid film formed by fuel droplet impacting on surface in small-size combustor of diesel engine, a numerical model was developed using volume of fluid method including heat transfer and contact resistance and verified by experiments. The mechanism of droplet fluid and heat transfer as well as breakup during spreading were obtained according to the result analysis. The results also showed that the droplet maximum spreading factor and heat flux at impacting point were closely related to impact velocity, and the dimensionless time of maximum spreading factor and constant heat flux are uncorrelated to impacting velocity. The amount of heat transfer linearly increased with Reynolds number. The theoretical analysis model was also developed based on energy conservation equation, which showed a good agreement with numerical results. 