The invention provides an unfolding device achieving high precision, miniaturization and high torque output. The unfolding device comprises a stepping motor, a planetary gear reducer, a harmonic reducer, a rotary transformer, an output shaft, a male hinge and a shell; the stepping motor is used for providing driving power, the planetary gear reducer and the stepping motor are of an integrated structure, and the planetary gear reducer is connected with the harmonic reducer; the output shaft and the harmonic reducer are of an integrated structure, the output shaft is connected with the male hinge, and the male hinge is used for being connected with a target load; a rotor of the rotary transformer is connected with the output shaft, a stator of the rotary transformer is connected with the shell, and the rotary transformer is used for achieving high-precision control over the output shaft. The unfolding device solves the problems that the requirement for the weight of a driving mechanism is high, the load is heavy, and adaptation to lunar surface high vacuum, large temperature difference and lunar dust environments can not be achieved, the problems cannot be solved in the prior art, and the unfolding device achieves the high precision and adaptation to lunar day working and lunar night existence.