Abstract: A well test model of injection well in low permeability reservoir is established in this paper, considering the characteristics of water-flood induced fracture and elliptical flow composite. Two mathematical model in Laplace space are obtained by means of dimensionless and Laplace transform. The bottom-hole pressure solution is obtained by introducing Mathieu function and the sample curve of pressure response is drawn, and six flow stages of the curve and characteristics of pressure propagation are clarified. Two injection well in J oilfield are chosen as example, a series of key parameters such as the half length of the fracture, the range of lateral wave affected area, the permeability in swept area, the mobility ratio and the distance of constant pressure boundary are obtained through model fitting inversion. The morphology of waterflood front and waterflood swept area are quantitatively characterized, the seepage law of waterflood and distribution of remaining oil in the case area are clarified based on the dynamic data, providing reference for the reasonable waterflood development plan with long-term stable production, which verifie the accuracy and superiority of the model.