The invention provides a charging-type caulking gun with an automatic pressure-relief function. The charging-type caulking gun comprises a caulking gun body, a bracket assembly, a piston rod and a charging base. The bracket assembly comprises a caulking agent cylinder; a first threaded pipe and a second threaded pipe are fixedly mounted at the left end and the right end of the caulking agent cylinder correspondingly; the first threaded pipe is connected with a first bracket connecting pipe in a threaded mode, and the second threaded pipe is connected with a second bracket connecting pipe in athreaded mode; a spraying nozzle is sleeved with the second bracket connecting pipe; a piston is arranged on the inner wall of the caulking agent cylinder in a sliding fit mode, and a groove is formedin the right end of the piston; and one end of a compressed spring is fixedly connected into the groove, and the other end of the compressed spring is fixedly connected with the piston rod. The charging-type caulking gun is simple and clear in structure and convenient to use; buffer between the piston rod and piston is achieved through the compressed spring, and a caulking agent is effectively prevented from being leaked after discharged; and four sets of guiding rods are mounted to be connected with the piston in a threaded mode, thus stress of the piston is even, uniformity of the pushed caulking agent is guaranteed, the discharging speed of the caulking agent is conveniently controlled, and thus the caulking agent is saved.