Abstract: China faces severe challenges from geological and geotechnical hazards, making disaster prevention and mitigation a national priority to ensure the safe operation of critical infrastructure. Understanding multi-field, multi-parameter geological information and its evolution under natural and anthropogenic influences is essential for effective risk reduction. Meanwhile, China invests substantial annual funding in geological drilling for surveys and engineering investigations, resulting in hundreds of thousands of boreholes. However, less than 0.1% of these boreholes are used for long-term monitoring, representing a significant waste of valuable monitoring resources. This study proposes a Geo Fiber Optic Sensing Network(GFOSN)framework based on 3D distributed fiber-optic sensing technology, utilizing existing geological survey boreholes. The sensing principles, features, and advantages of 3D distributed fiber-optic technology are introduced, and the basic components and system architecture of GFOSN are clarified. Furthermore, monitoring work conducted by the research group over the past decade using GFOSN is presented, covering applications such as land subsidence in the Suzhou-Wuxi-Changzhou area of the Yangtze River Delta, the Majiagou landslide in the Three Gorges Reservoir region, geothermal resources in Kunshan, seepage fields at the Zhinan Village levee in Zhenjiang, soil moisture dynamics in the Yan'an loess area, and multi-physical field monitoring in the deep drilling site at Jiajika in western Sichuan. These efforts have yielded a series of innovative results and are intended to advance the development of continuous spatiotemporal sensing technologies for hazard monitoring and early warning in China's geological and geotechnical engineering sectors.