A Fenton reactor, including a body. The body includes: from the bottom up, a sewage introduction zone, a solid acid reaction zone, tubular ceramic membranes, and a water generation zone. A water feed pump, a first chemical feed pump, and a second chemical feed pump are disposed below the body. The outlets of the water feed pump, the first chemical feed pump, and the second chemical feed pump communicate with the water inlet of the body. The water feed pump, the first chemical feed pump, and the second chemical feed pump are provided with flow meters, respectively. The solid acid reaction zone is disposed above the sewage introduction zone, and the tubular ceramic membranes are disposed in the center of the solid acid reaction zone and separate the solid acid reaction zone to form a cavity. The water generation zone is disposed above the solid acid reaction zone.