Disclosed is a quantitative liquid discharge device capable of discharging liquid in a container at a preset liquid level. The device comprises a liquid discharge pipe, an outer sleeve and a liquid level control rod. The liquid discharge pipe is provided with a full-discharge liquid discharge port and at least one internal defined-level liquid discharge port. Installed outside the liquid discharge pipe, the outer sleeve is provided with an external defined-level liquid discharge port. The wall of the liquid level control rod is slidably sleeved between the wall of the liquid discharge pipe and the wall of the outer sleeve. The liquid level control rod is provided with a liquid guide port passing through the wall thereof. Provided between the walls of the outer sleeve and the liquid level control rod a sliding positioning assembly allows the liquid guide port to achieve liquid discharge at a defined liquid level.
