Abstract: A method to analyz the heat transfer of greenhouse covering materials and computational method of overall heat transfer coefficient were put forward in this paper. And it is called the method of energy equilibrium in covering layer. Considering energy equilibrium of convection and radiation of covering layer in this method, a model of heat transfer comprehensively indicating main factors that affect the heat transfer of covering layer was established. And the analytic method to theoretically calculate the heat transfer was deduced. This method quantitatively analyzes the heat transfer of the covering layer, and then calculates the theoretical values of the overall heat transfer on the basis of emissivity of infrared radiation, reflectivity, transitivity and other thermal properties of covering materials, the ratio of the covering materials area to the soil area, angle coefficients and other constructive parameters of the covering layer, and internal and external air temperatures, sky radiation temperature, plant temperature, ground temperature in greenhouse, wind speed and other working conditions.