The invention discloses a direct-current power supply device and a charging circuit thereof. The direct-current power supply device comprises a side frame, a cabinet body, a cabinet door and a fan. A multi-layer battery device is installed inside the cabinet body. The battery device is composed of a battery supporting plate, and battery installation grooves fixedly arranged on the battery supporting plate in a matrix mode, the side frame is arranged on the left side of the cabinet body, the lower portion of the side frame is of a U-shaped structure, the U-shaped section of the lower portion of the side frame is plugged into a groove in the left side of the bottom of the cabinet body in a matched mode, a flange is further arranged on the left side of the top of the cabinet body, a bolt is arranged on the flange, the bolt is in threaded connection with a screw hole in the side frame, the top end of the side frame is further provided with an installation hole, and the right side of the cabinet body is provided with the cabinet door in a hinged mode through a hinge. The battery installation grooves can reinforce placement of batteries so that the phenomenon that the batteries are damaged due to short-circuiting caused by collision of the cabinet body in the moving process can be avoided, and external dust can be prevented from entering the cabinet body due to a dustproof net; in addition, on the basis of the charging circuit, charging can be automatically stopped after charging is finished, and the continuous using requirement of a power supply is met.