The invention discloses a mop cleaning barrel, and belongs to the technical field of cleaning devices. The mop cleaning barrel comprises a water tank with a water outlet channel; a cleaning barrel body, which comprises a water inlet seat and a cleaning seat, wherein the water inlet seat is connected with the cleaning seat, the water inlet seat is provided with a water storage cavity and a water outlet, the water outlet is located in the water storage cavity, the water tank is installed on the water inlet seat, a water outlet channel is communicated with the water outlet, the cleaning seat is provided with a water inlet, a clean water cavity and a sewage cavity, the clean water cavity is separated from the sewage cavity, and the water inlet is formed in the clean water cavity and is communicated with the water outlet through a connecting pipeline; and a cleaning disc, which is provided with an impeller cavity, an impeller, a water scraping part and a drainage part, wherein the impeller cavity and the clean water cavity are arranged up and down, the impeller is rotatably arranged in the impeller cavity, and the water scraping part and the drainage part are both located above the sewage cavity. The cleaning barrel body has the functions of dynamic water balance and clean water and sewage separation, water does not need to be added repeatedly when the mop is cleaned every time, water does not need to be changed many times, the mopping efficiency is improved, and water resources are saved.