Abstract: NXJ-type strain clamps are widely used in overhead lines of distribution networks, but with the increase of service life, the decline of wire grip force, loosening and slippage of insulated wire and other problems seriously affect the safety of distribution system, which may lead to serious consequences. Aiming at the NXJ-185-type strain clamp, the three-dimensional model is established by using the finite element software to simulate the stress distribution of the clamp in actual use in the static simulation, the failure causes are analysed, and the structural optimization scheme is put forward. The simulation results show that the non-uniform stress on the groove side of clamp wedge is the main reason for the failure of the NXJ-type strain clamp. On this basis, the optimization scheme is put forward, and the finite element software simulation development shows that the optimization scheme can effectively solve the problem of excessive stress concentration.