Abstract: An automobile breakdown warning sign includes a first, a second, and a third plates; one or a plurality of a set of light-emitting devices and a single chip controller being disposed on the first plate; both of the second and the third plates being each disposed with one or a plurality of a set of light-emitting devices, multiple electric connection portions, and one or a plurality of signal transmission module; all three plates being abutted to one another by their ends and electric connection portions to form a triangle frame for those light-emitting devices to become a triangle light-emitting unit; the single chip controller controlling those light emitting devices to alternatively flare while the signal transmission module sends a signal to be picked up by any following vehicle for providing early warning.