Abstract: The heat conductivity factor of the coating and the composite heat-transfer coefficient of the coating air gap are determined by means of relevant practice and linear interpolation together with simulation.Influence by the coating thickness on the cross section temperature gradient of the heavy-wall shell is analyzed.Also analyzed are the cross section temperature gradients of the shell with different technological parameters on the basis of actual operation status,resulting in determination of the coating thickness ranges for shells with different wall thicknesses.