The invention discloses an underground cavity intelligent filling system. The underground cavity intelligent filling system comprises a detection robot unit, a 3D printing robot unit and a centralizedelectric control unit. After the detection robot unit finishes scanning the underground cavity, a three-dimensional space model of the underground cavity is constructed, a central control computer ofthe centralized electronic control unit performs stress field calculation and analysis on the exterior of the three-dimensional space model of the underground cavity, and on the basis of the three-dimensional space model of the underground cavity, a supporting model is constructed on the stress concentration point position on the surface of the inner portion of the three-dimensional space model of the underground cavity according to the calculation and analysis results and the input safety factors in sequence to generate a space three-dimensional supporting model, and a 3D printing path is generated, and then the 3D printing robot unit prints the three-dimensional supporting entity in the underground cavity in a 3D mode, so that controllable supporting quality and controllable filling amount, higher filling efficiency and higher safety are realized, space reuse is achieved, and the underground cavity intelligent filling system is especially suitable for the filling and treatment of underground cavity.