Abstract: A one-dimensional difference model for unsteady heat transfer of wall in solar greenhouse was established to predict and evaluate the thermal performance of wall in solar greenhouse. On the basis of meteorological data and the change patterns, the methods of calculation for solar radiation on the surface of wall as the inner heat source of border node, and for inside and outside air temperature as boundary conditions in form of Fourier series were developed. A method named “training method” was created to determine the initial condition of wall, based on the effect of periodic environmental conditions. Forward elimination and backward substitution was presented to solve the system of difference equation efficiently. A method of calculation for heat release of wall in solar greenhouse was developed, and the corresponding computer program called RGWSQCR was finished. With the simulation program of heat transfer process of wall, the information about heat flux and temperature of any point in the wall at any time could be found. Then such information would be provided to analyze the thermal characteristics of wall in solar greenhouse comprehensively.