The hexagonal flange nut mainly includes a nut body. A flange surface is fixed at one end of the nut body, and a cap is fixed at the other end of the nut body. Since the cap is provided on the nut body, when using the hexagonal flange nut, it has Better sealing can effectively prevent rain, moisture, dust and other harmful substances from infiltrating into the nut body and prevent the nut body from rusting, thus greatly extending the service life of the hexagonal flange nut.