Abstract: In order to solve the problem that the traditional frequency domain reflectometry（FDR） method has poor effect in locating the weak local fault of 110 kV transmission cable, it proposes a FDR location technology for cable local fault based on Blackman-Harris window.Firstly, it introduces the theory and model of local fault location based on FDR.Secondly, based on the model, a Blackman-Harris window with simple form and superior performance is introduced to when localing fault location identification.Finally, the simulation analysis results show that compared with other common window functions, the proposed method is effective in locating local faults and can provide reference for power supply companies with similar problems.