The invention discloses a wall painting device with a liquid self-supply function. The wall painting device comprises a base plate, a stirring barrel, a pumping mechanism, a lifting cavity, polishingmechanisms, a smearing roller and a forward and reverse rotation motor; the stirring barrel is arranged at the upper end of the base plate; the pumping mechanism is arranged on the left side of the stirring barrel and comprises driven gears, a driving gear, a threaded sleeve, a second threaded rod, a piston, a cylinder, a rotating rod, a first liquid guide tube and a second liquid guide tube; thelifting cavity is formed in the left side of the pumping mechanism; rectangular grooves are formed in the left and right ends of the lifting cavity; a supporting plate is fixedly installed at the leftend of a moving block and connected with a protecting cover through a supporting rod, and the smearing roller is rotationally connected in the protecting cover; the polishing mechanisms are symmetrically arranged at the upper and lower ends of the protecting cover. The wall painting device is simple in structure, convenient to operate, capable of achieving paint self-supply and continuous supply,high in automation degree, high in painting efficiency and good in painting effect and greatly reduces manual labor.