The invention relates to a combination structure of a pedal and a mandril of a bike. The combination structure comprises the mandril, a clamping sleeve part and the pedal, the clamping sleeve part can be rotatably positioned outside the mandril in a penetrating and sleeving mode, the outer wall of the clamping sleeve part is provided with at least one hook claw, the pedal comprises a mandril penetrating pivot portion, the inner wall of the mandril penetrating pivot portion is provided with steps, and the hook claws hook the steps. According to the combination structure of the pedal and the mandril of the bike, the pedal is not combined with the mandril, therefore, the left-right width of a bike body can be decreased due to the fact that no pedal is arranged, the width of an external package box is specifically decreased, and then the wood volume number of the external package box is decreased; the stability of the bike body in the external package box is high, the using amount of buffering filler filled in the space can be decreased, the total weight of the packaged bike is further decreased, and the freight transportation cost is lowered; the pedal can be independently assembled by a user, and assembling is easy; the pedal can be stably combined in the clamping sleeve part, and therefore it is guaranteed that the pedal cannot be separated from the mandril; the user can freely select the style of the pedal according to the hobby.