Children bicycle chain cover is essential, the highest saddle height is equal to or greater than 560mm should be put in a children's bicycle disc cover or other protective device to cover the outer surface of the chain and the chain wheel on the meshing part, when the chain sprocket meshing at all when the disc cover in the diameter direction on the outer side of the chain and beyond, with other protective devices do not cover plate, it should be extended to cover the scope of the initial point into the sprocket chain on both sides of the sheet along the chain to at least 25mm. The highest saddle height less than 560mm children should be equipped with a bicycle chain cover, it is to complete the cover chain, sprocket wheel and the outer surface and edge, but also cover the inner surface of the sprocket and chain and sprocket teeth, to prevent the child finger into the hurt. Since children's bicycles are not used for riding on highways, they must be used under adult supervision when they are used, and they must not be ridden on highways.