Abstract: A reinforcement structure for bearings of a bicycle hub assembly includes a hub and an axle extends through the hub. A connection portion is defined in one end of the hub. A ratchet sleeve has a transmission portion located on one end thereof and a bearing is located in the transmission portion. Multiple slots are defined in outside of the transmission portion and the axle extends through the ratchet sleeve. A ratchet unit having multiple ratchet teeth and a ratchet ring which is connected to the connection portion. The ratchet teeth are engaged with the slots. The ratchet ring has multiple ratchet slots defined in the inner periphery thereof and the ratchet teeth are engaged with the ratchet slots. A positioning unit has a positioning member located on one side of the bearing so as to prevent the bearing from shifting axially.