The invention discloses a high-voltage line reactive power compensation device. The high-voltage line reactive power compensation device comprises a box body, a fuse, a first lightning arrester, a voltage regulator, a capacitor and a comprehensive monitoring and protecting controller; the fuse and the lightning arrester are electrically connected with the load side of a high-voltage line; the voltage regulator is connected with the fuse; a current transformer is arranged between the voltage regulator and the fuse; the comprehensive monitoring and protecting controller receives output signals of the current transformer and transmits a control instruction to the voltage regulator; the voltage regulator regulates voltage output and changes the voltage at the capacitor end, so that the output of the capacitance of the capacitor can be changed; and the voltage regulator has nine-level voltage output, so that the capacitor corresponding to the voltage regulator also has nine kinds of capacitance to perform reactive power compensation on the line. According to the high-voltage line reactive power compensation device of the invention, the magnitude of protecting current can be set according to the actual situation of the capacitor, so that accurate protection can be realized; no operating overvoltage is generated, no impact will be exerted on a power grid; and unified management and monitoring can be facilitated, and the unified monitoring on the compensation device can be facilitated.