Abstract: The peak moment is the main design index of a tape spring. Based on Calladine’s model to predict the peak moment of a bent tube, the analytical model for the strain energy and moment is built for the tape spring under opposite-sense bending, and the peak moment of the tape spring is predicted. It is assumed that the pure bending process of the tape spring can be divided into two stages: The cross section of the tape spring is firstly partially flattened, and the tape spring is secondly bent in the longitudinal direction. It is also supposed that a polynomial function is used to describe the deformation of the cross section during the first stage. The coefficient of the polynomial is solved based on the principle of minimum potential energy, and then the expression of the moment can be deduced, and the peak moment can be solved. A finite element model for the tape spring under opposite-sense bending is built using the commercial software ABAQUS to verify the reliability of the theoretical model by the comparison of the results from the numerical and analytical study upon the model proposed. By calculating the peak moment of the tape spring with different geometric parameters, the influence of the radius, of the central angle and, of the thickness of the cross section on the peak moment is investigated.