By parametric analysis of direct solar gain on building walls, equivalent decomposition was carried out for the direct solar gain. Upon this, building orientation transformation rules were proposed. Two types of buildings with different lengthwidth ratio in Shanghai were taken as case studies with simulation. And comparison curves of different orientation between transformation ones and the formers were obtained. It was found that cooling loads of transformed buildings were in good agreement with those of real buildings, which implied that the essential of orientation’s influence on cooling load was areas alteration of walls and windows in different orientations. By the transformation rules of building orientation, community buildings with different orientation can be transformed into those with the same orientation to predict community cooling loads, eliminating influences of the factor of building orientation.