This invention includes a first clamping means which comprises a base and a clamp for mounting a portable lighting apparatus; the clamp is mounted on a first end surface of the base; sliding slots are formed on two opposite side walls of the base; a second end surface of the base is provided with a groove; fixing rings, each of which comprises a connecting strip and first fixing members provided at two ends of the connecting strip; the connecting strips are mounted on the sliding slots for the base to slide on the fixing rings; a support comprising a body and a plurality of contact beads; the plurality of contact beads are mounted on the body by elastic members; a second clamping means comprising a fixing block and movable lock blocks mounted on two sides of the fixing block; the fixing block is mounted on the support.