In order to understand the pressure response characteristics during the CO2 flooding process and determine the location of the displacement front，a well testing interpretation method for the CO2 flooding displacement front is studied.Considering the effects of CO2 flooding mechanism，start-up pressure gradient，and heterogeneity characteristics of the lowpermeability reservoirs，a multi-component well testing model for CO2 flooding wells in low permeability reservoirs is set up. Based on the unstructured grid generation technique and the finite volume method，the nonlinear algebraic equations are solved by the Newton-Raphson method. According to the characteristics of the flow pattern，the well testing curves are divided into five sections：the wellbore storage section，transitional section，radial flow section of pure CO2 zone，flow section of CO2 swept zone and flow section of CO2 unswept zone. By tracing the effect of fluid property changes on the well testing curves，the effect of CO2 concentration changes on the pressure is further studied，and a method for determining the flooding displacement front is established. The field application practice shows that this method can be used to analyze the location of the displacement front，predict the advancement of the front，and provide an effective means for understanding the development law and optimizing the development scheme of CO2 flooding in low-permeability reservoirs.