The invention relates to a modularized series joint of a collaborative robot. The modularized series joint comprises a joint shell as well as a hollow motor, a harmonic reducer, an input shaft, an output shaft, a torque sensor, a brake, an absolute value encoder and a driver which are arranged in the joint shell, wherein the harmonic reducer, the hollow motor, the brake, the absolute value encoder and the driver are sequentially connected to the input shaft in series. A joint structure disclosed by the invention is more compact in structure, low in cost, higher in safety and reliability, ingenious, modularized and integrated; a brake structure is simple, convenient to install, reliable in brake performance, and stable; a force feedback system is sensitive in performance, stable, and high in reliability; and in addition, central hole wiring is used for wiring and arrangement, so that wire arrangement is more reasonable, and the wiring is more convenient.