In this paper, the mode jumping phenomenon in composite stiffened panels is studied using finite element method (FEM). Four cases of post-buckling behavior: local buckling, mode jumping, mixed buckling and global buckling was observed for different lengths of composite stiffened panels. To analyze mode jumping, the composite stiffened panels are divided into stringer area and skin area artificially. The linear buckling loads and mode shapes of stringer area and skin area are compared. Based on the buckling analysis about stringer area and skin area, three conditions are presented to predict whether the mode jumping occurs in the composite stiffened panels during post-buckling.