The invention discloses an anti-falling protective device of aloft work through a crawling ladder. The anti-falling protective device comprises a protective clamp; an axial guiding groove is formed in one side face of the protective clamp and used for being clamped onto a vertical rod of the crawling ladder, a through hole is formed in the position, at the bottom of the guiding groove, of the other side face of the protective clamp, and a cam mechanism is installed in the through hole; the cam mechanism is rotatably supported on the two side walls of the through hole through a positioning shaft, the inner end of the cam mechanism downwards rotates along with the cam mechanism to protrude forwards the guiding groove, and the inner end of the cam mechanism upwards rotates along with the cam mechanism to contract towards the internal the through hole; a cavity is formed in one side wall of the guiding groove, a rotating wheel is supported in the cavity, and at least three spokes are installed on the outer circumferential face of the rotating wheel; and the outer ends of the spokes protrude into the guiding groove to limit the vertical rod of the crawling ladder to slide out from the guiding groove and are installed to be opposite to the cam mechanism. According to the anti-falling protective device, effective anti-falling protection is provided for a worker, and crawling ladder climbing is not hampered, so that crawling ladder aloft work is greatly convenient.