Abstract：
In engineering design，the slope and the horizontal projection length of sloping layer are easily identified，but the thickness shall be obtained only by calculation of energy saving?郾 The sloping layer thickness is variable，and the calculation thickness is only average thickness?郾 The sloping layer thickness depends on the requirements of the roof energy saving?郾 It is important to thoroughly analyze the principle of roof heat transfer and to establish the mathematical model of roof heat transfer?郾 Then through rigorous mathematical calculation，the common law of how to determine the sloping layer thickness can be summed up?郾 According to the slope gradient，slope length and layer thickness calculation value，the maximum thickness and the minimum thickness can be ultimately determined，it provide the basis for construction site?郾
