The invention belongs to the technical field of electronics, and provides a bicycle speed meter with a warning effect. The bicycle speed meter with the warning effect comprises a speed meter body and a speed meter support, wherein the upper edge of the speed meter support is provided with a circular groove of which the circle center is a junction of upper edge rectangular extension sections; hinge pins are fixed on an upper groove wall and a lower groove wall of the circular groove; and the speed meter support is connected with a light-emitting device through the hinge pins. The problem that the bicycle speed meter in the prior art cannot emit light or reflect the light is solved. The light is transmitted through the light-emitting device and is reflected through a light reflecting material, pedestrians and drivers of vehicles are warned, and the bicycle speed meter is beautified.