Bicycle seat pillar

The utility model relates to a bicycle seat stand pipe, which is molded by composite materials. The stand pipe is inserted into a shaft tube of a bicycle frame. A locking and fixing member at the end of the shaft tube is locked outside the stand pipe. The interface of the stand pipe and the locking and fixing member is provided with a long strip-shaped groove, and a reinforcing piece is stuck and arranged in the groove for positioning. The reinforcing piece comprises an outer layer and an inner layer, the outer layer is flaky and is made of metal materials, and the inner layer of the reinforcing piece is made of composite materials. The utility model can prevent the stand pipe from being damaged, and can therefore, extend the service life of the bicycle seat stand pipe.