In order to improve the thermal rigidity of a large gear grinding machine, the effect of cooling liquid on its thermal characteristics was investigated through establishing the thermalstructure coupled finite element analysis method. The results show that the workpiece column and the column appeared “backward” phenomenon. This is because the cooling liquid absorpt grinding heet spray to the junction of front and rear bed, rotary table and three sides of workpiece column.Then there is a large temperature gradient in the direction of the length and height. With coolant temperature increases, the total relative deformation of spindle end and table center increases, maximum deformation is up to 1746 μm.