The invention relates to an unpowered automatic siphon water supply and drainage system. The unpowered automatic siphon water supply and drainage system comprises five parts of a low-area water source, a siphon pipe, siphon water flow control equipment, an exhaust one-way valve and water injection equipment, wherein the low-area water source comprises a water inlet pipe, a low-area water pool anda suction well with a filter screen; the siphon water flow control equipment is an automatic pressure relief valve; and the water injection equipment comprises a water injection pipe, a liquid level control valve, a siphon pilot valve, a water seal elbow pipe, a high-area water source, a hydraulic pipe and a pneumatic pipe, wherein the liquid level control valve is controlled by the siphon pilot valve, the liquid level control valve and the siphon pilot valve are connected by the hydraulic pipe, the hydraulic pipe is provided with a time-lapse self-closing valve, and the siphon pilot valve isarranged above the liquid level of the lower-area water pool. According to the unpowered automatic siphon water supply and drainage system, the elevation difference of all water inlet and outlet can be realized, an unpowered automatic siphon water supply and drainage function of occasions where the water level of some water sources is lower than water outlets can be realized, and the unpowered automatic siphon water supply and drainage system has a wide application range, and can be widely applied to the technical fields of municipal, industrial and building water supply and drainage.