When the plane valve of the water delivery system of a III-class ship lock is closed,the blockage occurs,resulting in the breakage of the boom.In this paper,dynamic principle and finite element method are used to analyze the causes of buckling failure of valve boom.Under the condition of water delivery valve blockage,the valve,boom and headstock gear form a planar four-link mechanism,which is easy to cause buckling failure of the boom under pressure at the collinear dead point.Through the calculation of linear buckling characteristic values and nonlinear post-buckling analysis,it is concluded that the critical buckling load of the boom is 80 kN,which is lower than the overpressure alarm value of the hydraulic headstock gear.The buckling mode shows that large deformation occurs after the boom is destabilized under pressure,resulting in plastic deformation and fracture of local materials after yielding,which makes the boom break.The critical buckling load of the boom is more sensitive to the material plate thickness of the hinged single lug plate.Increasing the plate thickness or using double lug plate structure can significantly improve the ability of the structure to resist buckling instability.The research results can provide reference for similar structural design.