Cable force estimation is essential for maintaining the structural integrity of a cable-stayed bridges. This study compares the effectiveness of vibration-based methods, particularly beam theory using least-squares and two-mode combination approaches, in estimating cable forces on the cable-stayed bridge. The analysis focuses on a pair of the longest and shortest cables located on the downstream side. Vibration data were recorded using accelerometers, and the natural frequencies were extracted using the Fast Fourier Transform. These frequencies were then applied to carried out the cable force. When compared with lift-off test results from 2017, the average deviations were 4.78% for the least-squares method and 5.06% for the two-mode combination. The findings indicate that both methods provide consistent and reliable estimates, especially for medium to high-tension cables. Slight discrepancies in certain cables suggest the need for further monitoring and validation. This research supports the application of vibration-based, non-destructive approaches for structural health monitoring in cable-stayed bridges and offers practical insights for maintenance planning.