The present utility model relates to a luminous caution light of a bicycle. The luminous caution light comprising an outer housing and a light-emitting screen installed on the surface of the outer housing is characterized in that the inside of the outer housing is fixedly connected with a hollow shaft, a stator coil is permanently installed on the hollow shaft, the stator coil is electrically connected with a power supply terminal of the light-emitting screen through a conducting wire in the hollow shaft, a permanent magnet is installed on the hollow shaft through a bearing, and the permanent magnet is fixedly connected with a counter weight block. The luminous caution light has advantages of simple structure, convenience in use, charging-free, long-term usage and active warning, greatly improving safety of running a bicycle in the nighttime.