The invention provides a multifunctional light-weight service robot joint module. The multifunctional light-weight service robot joint module is suitable for rapid manufacturing of a service robot mechanical arm. The module comprises an output end, a harmonic reducer, a flange, a hollow direct-current brushless motor, a hollow wiring pipe disc, a hall type absolute set zero disc, a photo-reflection type relative encoder and a control device. The control device comprises a control board, a direct-current brushless motor drive board, a communication assembly and multiple sensors; the hollow direct-current brushless motor drives the output end to rotate through the hollow harmonic reducer, the photo-reflection type relative encoder is used for measuring the output rotating speed of the hollow direct-current brushless motor, and the control device is used for controlling operation of the hollow direct-current brushless motor. The module size is close to the human body size, one-machine transmission is adopted, the structure is compact, multiple intelligent sensors are combined, the service industry application and intelligent integration are facilitated, and the problems that an existing integrated joint is large in size, heavy, poor in safety protection function and the like are solved.