When cracks occur in a helical gear pair,it can affect the meshing stiffness of the gear pair.In order to obtain a more accurate meshing stiffness of cracked helical gear pairs,an improved calculation model for the meshing stiffness of cracked helical gears was proposed,which comprehensively considered the effects of gear tooth stiffness and gear foundation stiffness in both the transverse and axial directions.The meshing stiffness of the gear system under two typical crack conditions of the tooth tip propagation crack and the end face propagation crack was studied,and the analytical calculation results of meshing stiffness were compared with the finite element simulation results.The results show that the degree of reduction of meshing stiffness is mainly related to the effective crack area.The larger the crack area is,the greater the decrease in meshing stiffness is.When the length and depth of cracks are the same,the effect of end face propagation cracks on meshing stiffness is more significant than that of top propagation cracks.The simulation results are in good agreement with the calculation results,which verifies the accuracy and effectiveness of the proposed method.