Abstract: Probing into pressure gradients for steam injection is of great significance to realize efficient and economic injection.Based on the international calculation for thermodynamic properties of steam and the basic equation for steam injection,the author calculates the pressure gradient of the two-phase wet steam flow and decomposes the gradient by using the homogeneous model of the two-phase flow theory.What’s more,corresponding program on the calculation of pressure gradients of two-phase flow is developed according to the theory of calculation for thermodynamic properties of steam.Calculation of actual steam injection shows that the change of pressure gradients is completely in accordance with the two-phase flow theory.