A car light is equipped with a supplementary light for helping alert people to the car, which supplementary light includes several light sources, plane lenses, and a circular lighting body; the light sources are secured on a rear cover of the car light; the plane lenses are disposed over the light sources; the circular lighting body is fitted on a circular trench formed around the car light, and has spaced condensing bumps on an outer side thereof; the plane lenses face respective ones of light passages formed on the trench; when the light sources are powered, light will be first made to travel through the light passages, and onto the circular lighting body by means of the plane lenses, and the circular lighting body will refract the light so as to shine with a complete circle-shaped light thereon.