Abstract: Dispersion and accumulation of hydrocarbon are complex processes in the evolution of a petroliferbus basin. Practical mathematical model of dispersion and accumulation of hydrocarbon, including estimating amounts of oil and gas expulsion, residual oil and adsorbed gas in carrier beds, solution gas and diffusion gas in reservoirs were presented in this paper. Considering the amounts of oil and gas expulsion, the amounts of dispersion and accumulation, and the volume of traps, a material balance equation in a play was set up. Which is a practical method for the evaluation of oil and gas resources.