Abstract: In order to investigate on buckling behavior of some composite cylindrical shells considering multimode imperfections, linear buckling analysis was performed for the perfect cylindrical shell under axial compressed condition to obtain the first fifty buckling modes, defined as mode imperfections. Nonlinear buckling analysis of the cylindrical shell under different mode imperfection was proposed based on the Riks method. Buckling loads calculated using finite element analysis results and empirical method results according to NASA SP-8007 were compared with Bisagni's test results. The results show that the first mode imperfection is not the worst imperfection for composite cylindrical shells under axial compressed condition. Buckling load obtained from the first mode imperfection is much higher than the experimental result. And buckling load obtained from higher mode imperfection agrees well with the experimental result. The decrease of buckling load is influenced by shape and amplitude of imperfection synchronously. The multi-mode effects should be considered on buckling analysis of composite cylindrical shells. Buckling load obtained from NASA is very conservative, which is much lower than the test result. Designing composite cylindrical shells according to NASA always results in heavy structure, material redundancy and poor performance.