Considering the weakness of interlayer in traditional composite π-joints, a novel composite π-joint structure is proposed, and joints with different panel thickness are manufactured by prepreg-RTM method. Flexural experiments are tested on composite and aluminum joints, the results show that the flexural strength of composite joints with 6 mm bottom panel thickness are better than that of aluminum joint, and the flexural stiffness is in the same scale. For the joints with 8 mm bottom panel thickness, the flexural strength of composite joints are less than that of aluminum joint, and the flexural stiffness is also in the same scale.