The installation error and axial deformation of gear exist in the actual working conditions,result in partial load and affect contact state and fatigue performance of gear. The research of the fatigue performance of herringbone gears under variable load when considering the effect of installation error and axial deformation is one of the difficult problems in the design of herringbone gear. A method for analyzing the fatigue performance of herringbone gears under the variable load and actual working conditions is proposed. The modeling method of finite element contact analysis model considering the influence of installation error and axial deformation is proposed. The calculation of the partial load of herringbone gear under the actual load condition based on the finite element contact analysis model. The safety factor of contact strength of the gear is calculated based on the stress results of loading contact analysis and load spectrum. The work of this study provides a useful reference method for the design and analysis of high performance herringbone gear.