Abstract: A quantitative analysis method of aerodynamic interferences on aerostatic coefficients of twin separated decks was developed. Interference factor (IF) was defined as the ratio of aerostatic coefficient of twin decks to that of single deck. Aerodynamic interferences on aerostatic coefficients of bridges with twin decks were studied using three representative sections (rectangular section, Π shaped section and streamlined section) through pressure-measured wind tunnel experiments. The experimental results show that aerodynamic interferences on aerostatic coefficients are mainly attributed to shielding effect. Mean value of drag coefficient of leeward section is smaller than that of single section. Compared with streamlined section, shielding effect on bluff sections (rectangular section and Π shaped section) is more significant.