Abstract: There are few studies on the allowable differential air pressure between compartments in suction installation and leveling conditions of composite bucket foundation. Taking the installation of composite bucket foundation in an offshore wind power project as the background,the quantitative analysis of allowable differential air pressure of leveling Δp for composite bucket foundation at different installation depths is carried out by using ultimate stress control method,the critical differential air pressure of the bulkheads yield of the model with and without soil modeling is calculated by numerical simulation method,and the selection method of allowable differential air pressure during leveling of composite bucket foundation is proposed. The results show that the minimum value of ultimate stress and buckling of the bulkheads should be selected for the allowable differential air pressure of leveling during the suction installation,the reinforcing ribs of the bulkheads can effectively improve the allowable differential air pressure of leveling Δp,it is recommended to use the model with soil modeling to calculate the allowable differential air pressure of leveling.