The boundary condition of the cable in the cable net structure is usually not an ideal hinge, but a semi-rigid constraint with unknown boundary stiffness. In order to accurately identify the cable force in the cable net structure, this paper proposes a cable force identification method considering semi-rigid constraints at both ends. Firstly, according to the string vibration theory and the single-degree-of-freedom system model, the calculation formula of cable force under semi-rigid constraints is derived, and then the accuracy of the proposed method is verified by a numerical example of a single cable. The results show that for the cable with semi-rigid constraints at both ends and the numerical model, the error of the cable force identification results obtained by the proposed method is within 1%.Therefore, the cable force identification method considering the semi-rigid constraints at both ends improves the accuracy of the traditional cable force identification theory, avoids solving the unknown boundary constraint stiffness, and considers the complex and changeable boundary effect of the cable, which can meet the needs of cable force identification accuracy in practical engineering.