The building total load index of the office buildings in Harbin, Lanzhou, Chongqing and Guangzhou were assessed by the analytical hierarchy process based on the effect of single factor on the building total load index to study the synthetic effects of several factors on the total load index of the office buildings in four climate zones. The weights of varied indexes of window heat transfer coefficient, glass sunshade coefficient and window-wall ratio were determined by the analytical hierarchy process. And the consistency of the weight of index was checked ultimately. The results indicated that the importance of the three factors for the total load index of the office buildings in Harbin and Lanzhou was R > K_w > S_c, while the importance of the three factors for the total load index of the office buildings in Chongqing and Guangzhou was S_c > R > K_w. In the optimum design of building structure, the crucial factors should be controlled preferentially for a building in different climate zones.