The invention relates to a bike centre shaft which comprises a shaft body, a pillow block, a ball bracket, a clamp spring groove and a square wedge, wherein the ball bracket is a smooth arc used for matching and connecting with a bearing inner ring, the ball bracket is arranged between the pillow block and the clamp spring groove, the inner part of the square wedge is provided with a bolt hole, and the inner wall of the hole is provided with a thread. The centre shaft changes the way that the original ball bracket is used for arranging steel balls and matching with a shaft bowl into the way that the original ball bracket is matched with a bearing, thereby having convenient assembly and use, high coaxiality, good sensitivity and durability.