Abstract: To predict fatigue life under multiaxial variable amplitude loading at high temperature,the stress amplitude was used as damage variable and multiaxial fatigue damage was computed with classical Chaboche model.Determination of equivalent stress under multiaxial loading was based on the constitutive relationship under uniaxial loading and the equivalent stress was obtained with multiaxial equivalent strain.The expression form of stress index in the Chaboche fatigue accumulated damage model was revised.Fatigue damage under variable amplitude loading was solved according to the Chaboche damage accumulation model.Chaboche fatigue damage cumulative formula under multistage loading was deduced and applied to fatigue damage evaluation under variable amplitude loading.The life prediction results close to the experimental results.The error is basic within 2 time factors,indicating the feasibility of the life estimation method.