Abstract: Abstract: All the bolts & nuts of turbine low pressure cylinder cross-over pipe being seizure during every time dismantling in a nuclear power station, then have to cut off. This paper raise a extensive analysis including bolts & nuts material and mechanical performance, bolt preload and torque, bolt tightness manner, combine with FEA and torque coefficient practise test, the root cause of bolts seizure is that during tightening bolts with hydraulic wrench with a reaction arm, some thread teeth local area stress beyond the material yield strength when the torque reach some extent, then resulting to plastic deformation. The bolts & nut never seizure again after implementing the solution that presented in this paper. The research described in this paper have some reference meaning for solving various fasteners seizure problem in nuclear power station. Key words: bolts seizure; torque; tightening manner; lateral offset force; excessive stress; torque coefficient