With the rapid development of high-voltage transmission lines in China, traditional deformation monitoring technologies face challenges such as limited accuracy and poor adaptability to complex environments. These limitations become particularly evident in regions with complex terrain or severe weather conditions. To address these challenges, we introduce multifrequency Global Navigation Satellite System (GNSS) technology as a solution to enhance both the accuracy and efficiency of deformation monitoring for large-scale power infrastructure, especially high-voltage transmission line towers. We implement multifrequency GNSS technology for the long-term, all-weather monitoring of transmission line tower deformations. By integrating GNSS data quality analysis, we propose a customized monitoring solution tailored for large-scale power infrastructure. To evaluate the effectiveness of multifrequency GNSS, a comparative analysis is conducted against traditional dual-frequency GNSS technology, and the improvements in positioning accuracy and reliability are assessed. The results demonstrate that multifrequency GNSS significantly enhances the deformation monitoring precision. In particular, BDS triple-frequency solutions improve accuracy by 40.57, 44.5, and 36.8% in the E, N, and U directions, respectively, compared with dual-frequency solutions. Similarly, GPS triple-frequency solutions achieve improvements of 43.29, 43.45, and 37.2%. Moreover, both BDS and GPS triple-frequency solutions achieve a positioning accuracy of 3 mm in the horizontal direction and 5 mm in the vertical direction, maintaining stable performance over multiple days. These findings underscore the significant practical advantages of multifrequency GNSS in ensuring high-precision deformation monitoring for large-scale power infrastructure.