Disclosed are an underground displacement three-dimensional measurement system and method based on a double mutual inductance voltage contour. The system comprises an on-site measuring device and a remote monitoring system. The on-site measuring device is mainly formed by serially connecting N sensing units and an underground displacement information lumping unit by means of a power line and a communication line. The N sensing units are serially connected, and then are connected between an underground immovable layer and the ground. Each sensing unit comprises a PVC sleeve, a cylindrical air-core coil, a cylindrical magnetic core coil, and a PCB. Two adjacent sensing units form a measurement unit, and relative horizontal displacement and relative vertical displacement are measured by means of cooperation between the cylindrical air-core coil and the cylindrical magnetic core coil of a relative reference unit and the cylindrical air-core coil of the relative displacement unit.