The invention discloses a low-voltage ultralow-speed high-precision servo motor, and belongs to the technical field of motor equipment. The low-voltage ultralow-speed high-precision servo motor comprises a gapless magnetic brake, a front connecting flange, a public flange, an inner front motor bearing, a motor stator, a rear motor end cover, a rear motor bearing, a hollow inwardly concave rotor core, a front embedded bearing, a rear embedded bearing, a multi-bit hollow absolute value encoder, a small speed reducer, rear cover connecting pan head screws, public flange connecting pan head screws, brake connecting inner hexagonal screws, encoder connecting inner hexagonal screws and speed reducer connecting inner hexagonal screws. The low-voltage ultralow-speed high-precision servo motor hasthe advantages that a rotor is of a concave structure and is provided with output shafts, the small speed reducer is integrated inside the concave rotor and is connected with the inner wall of the concave rotor in a supported manner by bearings, the high-precision hollow encoder is arranged on an output shaft side of the speed reducer, an output shaft is connected with the gapless magnetic brake by keys, and accordingly the high positioning precision and stability precision can be guaranteed when systems run at ultralow speeds.