The invention relates to a valve, in particular to a combination seal fixed ball valve after the seal of the ball valve is improved. The invention comprises a valve body, a valve core, an open-close shaft and a seal valve base; the invention is characterized in that the valve body is composed of an upper valve body and a lower valve body; the ball valve core and the seal valve base are arranged in the hollow cavity between the upper valve body and the lower valve body; the open-close shaft is arranged on both sides of the valve body; the valve core is the single channel fixation structure; the open-close shaft is threaded through the valve body to be arranged on both sides of the valve core; the seal valve base is the combination of hard seal and flexible seal; wherein, the hard seal is the first seal and used for retaining and removing the particle medium, and protecting the second flexible seal. The combination seal fixed ball valve enables the seal level to reach zero leakage and enables the valve to be applicable to a variety of mediums and avoid valve deadlock, inadequate opening and closing situations so that the service life of the combination seal fixed ball valve can reach more than 0.2 million times.