The invention relates to a direct-hanging type reactive power compensation device and method based on a 10kV power grid. The device comprises a current transformer, a voltage transformer, an AD sampling plate, a master control device, a voltage zero cross detection circuit, a communication control device, a pulse generator, a pulse distribution plate, an SPWM signal transmission circuit, two H-bridge cascading inverter circuits, a filter, a PLC, a touch screen and an IO plate. According to the direct-hanging type reactive power compensation device based on the 10kV power grid, the direct-hanging type is indicated by the fact that direct synchronization can be carried out on the alternating current side of a topological structure through an electric reactor in a power grid system, and the synchronization is not required to be achieved through a transformer. A compensation command current detecting algorithm with an improved ip-iq method is adopted, the phase angle value phi when the system voltage jumps is added in the reactive current detection process, and therefore the system voltage in any state can be detected. Meanwhile, a structure composed of a DSP and two FPGAs is adopted, so that the aim of rapid dynamic compensation of the device in the performance is achieved.