The invention relates to a water level sensor, belongs to the liquid level sensor technical field, and mainly aims to solve the sensor failure problems caused by severe usage conditions in an auxiliary water tank, sensor capillary penetration and electrode corrosions; the main features are that the water level sensor comprises a wire harness assembly, a circuit relay assembly and a titanium alloy body assembly; the titanium alloy body assembly is formed by two symmetrical titanium alloy rod assemblies through injection moulding; the titanium alloy rod assembly comprises a wire, a copper insert and a titanium alloy rod, wherein the surface is coated with a conductive silver adhesive; the circuit relay assembly comprises a housing, a circuit board and a cover plate; wires of the wire harness assembly and the titanium alloy rod assembly are welded on the circuit board. The water level sensor uses the titanium alloy rods as electrodes; the sensor processing circuit and electrodes are integrated in a split mode, thus overcoming the auxiliary water tank severe conditions; the water level sensor is corrosion resisting, electrolytic resistant, high temperature resistant, non-adsorptive, and mainly applied to domestic Dongfeng warrior vehicles.