Abstract: An improved multifunctional pedaling motion bicycle, particularly to a transmission mechanism of bicycle includes a clutch member that is manually controlled to move between and selectively engage primary and secondary control blocks to perform different modes of operation of the bicycle, including regular pedaling, independent pedaling of cranks, same-direction upward/downward movements of the cranks. The transmission mechanism has a simple and light-weighted structure and thus low cost and low failure risk with extended service life. Further, a variety of different operation modes can be performed without dedicated rear hub.