The utility model discloses a novel self-lock device. The novel self-lock device comprises a braking main body, a handrail and an auxiliary braking block; a through groove is formed in the braking main body from the right lateral wall to the left; the braking main body is provided with a through hole which penetrates the rear lateral wall from the front lateral wall to the rear; a shaft II is inserted inside the through hole; the left end of the braking main body is provided with a fixing hole; the lower end of the handrail is fixed at the top of the braking main body; a shaft I is inserted in the upper portion of the auxiliary braking block from the front lateral wall to the rear lateral wall; rolling wheels are respectively fixed at the front end and the rear end of the shaft I; the middle of the shaft II sequentially penetrates the lower portion of the auxiliary braking block and a main body and a press spring; the upper end of the press spring is presses the left lateral wall of the auxiliary braking block; the lower end of the press spring presses the braking main body. The novel self-lock device effectively overcomes the defects that the existing power transmission overhead line falling-proof device is simple in insurance, long in cushion stroke and the like.