A bicycle crank speed change sprocket module includes a fixed star gear having a ratchet around its internal periphery, at least two planet gears and two chains pivotally coupled and axially disposed on both sides of a plate, and the plate is driven to rotate by a crank pedal, and the fixed star gear is engaged to the ratchets on the internal periphery of the planet gear and acted by the planet gear for a faster rotation; a freewheel sprocket freely and rotably coupled to the axle of the crank pedal and disposed proximate to the two chain wheels; and a ratchet disposed on the external periphery of the freewheel sprocket, a chain wound thereon, and the chain is engaged by at lest one chain gear, so that the rotary speed of the chain is much faster than that of the crank pedal for a speed change effect.