Abstract The action principle of squib valve employed in passive nuclear power plant was introduced and the main factors affecting the reliability of the mechanical components of the squib valve were analyzed, and the shear cover material of the squib valve was subjected to different strain rates at normal temperature, 155 °C and 350 °C, The parameter distribution of Johnson-Cook constitutive model was obtained by fitting the test data, and the impact velocity, material properties and failure strain of the squib valve piston were selected as random variables, and the reliability of the mechanical components of the squib valve was calculated by the joint simulation of ABAQUS+NESSUS. The results show that the reliability of the squib valve is high, and the mechanical performance of the shear cap material is the biggest impact on the mechanical reliability of the squib valve. The mechanical reliability of the squib valve is positively related to the impact speed of the piston. This study provides a reliable basis and reference for quantitative assessment of the overall reliability of the squib valve and the application in passive nuclear power plant.