A mechanical transmission module has two plates, a transmission mechanism and an actuating axle. The two plates are mounted together with a gap formed between the plates. The transmission mechanism is mounted between the plates. The transmission mechanism can be a Geneva mechanism, a worm and gear mechanism, a belt drive assembly, a threaded rod and slide mechanism, a geared mechanism and so on. The actuating axle extends out from the two plates and drives the transmission mechanism. A connector is secured to a free end of the actuating axle. The connector has a groove and a protrusion in the external face to engage with the groove and protrusion on the connector of another mechanical transmission module. Accordingly, the transmission mechanisms can be modularized and combined with each other. The combination and transmission relations between different types of transmission mechanisms are easily be understood through use of the modules.