The invention discloses a measuring device for underground space three-dimensional information and a detection method thereof. The device comprises a sensor system, a power system, a housing protection system, and a conduction system. The housing protection system comprises two constituent parts of a sealed upper metal housing and a lower metal housing. The power system comprises a motor, a signal emitter, a magnetometer, a gyroscope and a circuit board. The sensor system comprises an ultrasonic transducer, a temperature sensor, and a video sensor. The conduction system comprises a metal contact pin, a gear, and an upper end cap whose upper part is connected with a hoisting cable. The metal contact pin is arranged on the top end of the metal housing. The device can realize monitoring of a three-dimensional shape of an underground cavity under high temperature and high pressure states, and obtained cavity shape information has important significance on underground structure stability evaluation. The detection method is completed by the detection device, and the method is simple in operation, and can effectively detect three-dimensional space information of an underground cave under high temperature and high pressure states.