Great emphasis has been placed on steam flooding frontier. Most researches consider the steam overlap and pseudo mobility ratio. But heavy oil is non-Newton fluid, oil threshold pressure gradient is not taken into account. In order to study the steam flooding frontier of non-Newtonian heavy oil, the dynamic point contact with the cap rock of steam flooding frontier is present first. And then a mathematical model for steam flooding frontier considering oil threshold pressure gradient is established. The steam zone is obtained by difference and programming with Matlab. The results show that the greater the threshold pressure gradient, the smaller the dynamic contact point. And increasing the shape factor or decreasing the pseudo mobility ratio can reduce steam override degree and increase steam sweep efficiency.