The utility model discloses a liquid filling device of a lithium battery electrolyte, which comprises a liquid receiver filled with electrolyte, and a sucker with one end inserted into the bottom of the liquid receiver, and is characterized in that: the other end of the sucker is communicated with a liquid pumping mechanism and a liquid filling mechanism by pipelines sequentially, the liquid pumping mechanism mainly comprises a filter, a buffer tank and a liquid pump, the sucker is communicated with an inlet of the filter by a pipeline, an outlet of the filter is communicated with an entrance at the bottom part of the buffer tank, a liquid pumping port and a liquid filling port are respectively arranged at the top part of the buffer tank, and the liquid pumping port is communicated with the liquid pump; and the liquid filling mechanism comprises a liquid outlet pipeline and a filling pump disposed in the buffer tank, the bottom end of the liquid outlet pipeline is positioned under the liquid level of the buffer tank, the top end thereof is in sealing connection with the liquid filling port, the liquid filling port is connected to the filling pump by a pipeline, and an outlet of the filling pump is communicated to a filling opening of the lithium battery. The utility model can prevent impurities and air bubbles in the electrolyte from entering the lithium battery, thereby ensuring the performances of the lithium battery.