Abstract: In the construction of a new power system, the number of devices for monitoring the distributed conditions increases significantly, and the maintenance cost of power supply units rises. The future grid condition monitoring and sensing network has higher requirements for stability, reliability, and economy of power supply. Compared with transmission and battery power supply technologies, energy-harvesting power supply technology has the advantages of higher reliability, broader application scenarios, and lower maintenance costs, thus it will be one of the most promising suppy approaches. Firstly, we analyzed the current status and difficulties of power supply technology for grid condition monitoring devices. Then, we reviewed the mainstream self-harvesting technologies in two main categories, namely, the internal and the external energy harvesting. Among them, magnetic energy harvesting, electric energy harvesting, and triboelectric nanogenerator were highlighted. These three technologies have various structures, high power density, and broad application prospects. Furthermore, we summarized and analyzed the technical difficulties of the self-harvesting technology in terms of power supply reliability, output power, device robustness and service life, and the related technological progress and research directions. Finally, we discussed the significance and research direction of multimode energy harvesting, and investigated the development trend of power supply technology of condition monitoring devices.