Abstract: A 3D initial st ress analysis model of composite flywheel fabricated by filament tension winding was putforward by using the idea of the former plane st ress full elastic model. Based on the arithmetic of face to face contact , a 3D numerical method of calculating the initial st ress was proposed for composite in tension winding. The result s show that the numerical values of hoop initial st ress and radial initial st ress calculated by the 3D model are allsmaller than those obtained with the plane st ress model , and the difference increases slowly with the increase of theaxial length of the flywheel. The 3D analysis confirms that the plane st ress full elastic model has enough calculationprecision. The characterization and calculation method of the axial length effect of the 3D model is established.