A liquid storage tank is disclosed, including a primary tank, a secondary tank and a stirring device, the primary tank is arranged on the secondary tank and communicates with the secondary tank through a first valve, the stirring device is arranged on the primary tank, the stirring blade of the stirring device stretches into the primary tank to stir the liquid stored in the primary tank, the lowerend of the primary tank is provided with a liquid inlet port and the upper end is provided with an air outlet port, and the lower end of the secondary tank is provided with a liquid outlet port. Theliquid storage tank of the invention can store the electrolyte and separate bubbles from the electrolyte before liquid injection of the lithium battery, thereby effectively improving the liquid injection efficiency and improving the performance of the lithium battery. In addition, the invention also discloses a lithium battery liquid injection system capable of separating bubbles from an electrolyte and having storage and liquid injection functions at the same time.