With foam is widely used in the oil extraction, various methods involving the numerical simulation of foam flow in porous media are appeared. Therefore, the research on the characteristics and mechanism of the foam in the oilfield is definitely necessary. Based on the physical properties of foam, coalescence mechanism and oil displacement mechanism of foam flooding, an equivalent mathematical model of the technology is developed. The parameters for the model are corrected by the value of the resistance factor. The solution of the mathematical model is obtained by using IMPES method. Through the typical example, the equivalent mathematical model is proven to be feasible. The calculation conditions for the typical example are given. Double tube core flooding is simulated, and then the displacement effects between foam flooding and non-foam flooding are compared with each other. The core pressures of water flooding and foam flooding, saturation distributions as well as flooding efficiency are compared, the model is proven. The results show that the foam possesses a good plugging capacity to the layer with high permeability and the oil recovery could be efficiently enhanced by the foam flooding.