The invention discloses a contact type hydrostatic level, a relative subsidence monitoring system and method.The contacttypehydrostatic level comprises apull wire displacement sensor, a data acquisition module, a piston block, a Hookean elastic member, and a cylinder body;the pull wire displacement sensor is used for measuring the distance from the piston block to the pull wire displacement sensor, and the two ends of the Hookean elastic member are connected withthe piston block and the bottom wall of an inner cavity; the relative subsidence monitoring system comprises a liquid storage container, the contact type hydrostatic level, a data gathering device, and a data processing center, wherein the liquid storage container and the contact typehydrostatic level are connected to form a communicating vessel; and the relative subsidence monitoring method comprises the steps that through readings on the pull wire displacement sensor before and after subsidence of monitoring points, the liquid level difference with respect to the liquid storage container before and after the subsidence is calculated so as to calculate the relative subsidenceamount between the monitoring points. Accordingto the contact type hydrostatic level, the relative subsidence monitoring systemand method,subsidence of the monitoring points is converted into elastic deformation of the Hookean elastic member, thesubsidence amount is calculated through the deformation amount, and alarge measuring range can be realized whilehigh-precision of the hydrostatic level is ensured.