The invention relates to an extendable safety fence warning illuminating device. The device comprises a conical barrel main body, the conical barrel main body comprises a left part and a right part, the left part and the right part are connected through an extendable connecting rod, a connecting piece is arranged at the upper end of the left part, a matching piece of a connecting piece is arrangedat the upper end of the right part, and a flash lamp is arranged above the matching piece. The device has the advantages that the integration of two safety tools is realized, the use and management efficiency of the tools are improved, and the safety management and control effect of a construction site is improved; the night warning effect of a conical barrel is strengthened, and the night safetywarning effect of the conical barrel is further improved; the prompting function on the working area and content is also achieved at night; and an electric power storage module is kept at a certain distance from a pavement, so that the conical barrel can still keep illumination and power supply on a slightly waterlogged pavement.