The utility model provides an underground liquid level monitor for a gas storage well, which has long service life and convenience. The underground liquid level monitor is characterized by comprising a shell structure and a circuit structure, wherein the shell structure, in a cylindrical shape as a whole, consists of a cable fixed joint, a cable head protective barrel, a cable head socket joint, an insulating barrel, an electrode and a tail pipe which are sequentially connected; and the circuit structure comprises a cable and a detection circuit, the cable is fixed in the cable fixed joint and connected with the detection circuit, and the detection circuit is arranged in the insulating barrel and connected with the electrode. The working principle of the underground liquid level monitor is based on the conductive difference of saline water and diesel oil (or nitrogen gas), and the electrodeplate of the immersed saline water can be determined according to a current value output by the underground liquid level monitor, i.e. the one-to-one corresponding relation of the current value and the depth of an oil-water interface can be established, thereby the height value of the oil-water interface is determined. The underground liquid level monitor has higher bearing capacity without special molds, convenience for processing and manufacturing, long service life and lower cost.