Building energy conservation is the focus of attention in the whole society since high energy consumption of rural buildings is still severe. Most previous studies on energy conservation of buildings mainly focus on the quantitative analysis of a single factor, while the overall trend, significance, and priority of different combination factors influencing building thermal load are unclear. Taking rural buildings in the Hetao Area of Inner Mongolia as research objects, the influence rule of building envelope was studied on building thermal property through orthogonal test, energy consumption simulation, and multiple regression method. The results show that the priorities of building design factors in the Hetao Area of Inner Mongolia are sunspace depth > insulating layer thickness >transparent building envelope > exterior wall structure > building orientation > window-wall ratio; the building thermal load is minimum when the sunspace depth is 1 m, the insulating layer thickness 70 mm, and the window-wall ratio 0.5; and after optimization and reconstruction, the rate of energy conservation in Hohhot, Baotou, Bayannur, and Erdos is 67.5%, 69.2%, 72.8% and 76.5%, respectively, thus providing the decision basis for analysis on the quantitative law of spatial envelope structure factors and the parameter optimization.