Abstract: The fracture of a spring in manipulating pedestal of a main throttle valve used for steam turbine was studied.Both of composition and microstructure are qualified for the national criterion.The fracture mechanism of the spring is fatigue fracture.The main reason of the early fatigue fracture arose from the surface corrosion of the spring,which occurred during the placement before use.This problem cab be solved by improving the placement environment and shortening the placing time.