The invention discloses a waterproof device of a civil new-energy power generation box. A casing and flashings are included, the upper surface of the casing is provided with a square groove, chutes communicated with the groove are formed at the two sides of the groove symmetrically and respectively, a mount is installed in the middle portion of the upper surface of the groove by welding, an abutting rod is integrated and welded to the lower surface of the mount, a slide plate is arranged in the chutes in a sliding way, and support bars are mounted at one side of the slide plate symmetrically in a hinging manner; one side of the casing is provided with a water service pipe connected with the groove, rainwater falls into the groove can be output via the water service pipe, and the flashingsare arranged symmetrically in a rotational manner at the two sides to prevent rainwater from overflowing out of the front end; and when the flashings are needed, the support bars hinged to the surfaces of the flashings are pushed forwardly, so that the slide plate arranged in the end portions of the support bars is clamped in the side surface of the abutting rod, and the slide plate arranged in the sliding manner via the chutes slides to change the position.