Aiming at the problem of insufficient understanding of thin and poor reservoir waterflooding development, 40 phase permeability curves with thin and poor reservoir characteristics are screened out by collecting relevant in⁃situ permeability and reservoir physical properties data, and these permeability data are processed and analyzed by using statistical principle and method. The results show that the permeability curves of thin⁃difference reservoirs are mainly of three types: convex, concave and straight⁃line. According to the permeability distribution range of thin and poor reservoirs, the permeability curves can be divided into four permeability levels: below 10 mD, 10~100 mD, 100~200 mD and above 200 mD. The typical permeability curves of the same permeability level are analyzed, and it is concluded that the permeability characteristics of thin and poor reservoirs generally present the characteristics of "double high and double bottom". By analyzing the permeability curves and their characteristic parameters of thin and poor reservoirs with different permeability grades in different development stages, it is concluded that the permeability curves of different permeability grades will have different changes and effects under long⁃term water injection conditions, on the one hand, the enlarged and beneficial effects of phase permeability, on the other hand, the reduced and adverse effects of phase permeability.