Abstract: As composite is widely adopted, more and more hat-stiffened composite panels are used in aircraft structures. In order to investigate the loading capacity of hat-stiffened composite stiffened panel under axial compression, hat-stiffened composite panels with different radius of skin, thicknesses of skin and distances between adjacent stringers were tested under axial compression firstly. The relationships between local buckling load, collapse load and curvature coefficient of stiffened plate, distance of adjacent stringers were obtained. Then, by introducing curvature modifying coefficient, the existing buckling load formulation for engineering estimation of stiffened panel was modified. Finally, the engineering approach for ultimate load of stiffened plate under axial compression was modified using multistage operation method and combining effective width concept. The results show that local buckling load and ultimate collapse load of hat-stiffened composite panel are positive correlated with curvature coefficient. The modified method can predict the ultimate load of stiffened composite panel accurately. The conclusions obtained show that the modified approach can provide a new method for structural design and estimation for load of stiffened composite panel, which has definite engineering application values.