The utility model discloses an automatic upper base pulp grinder, including sizing agent tank, be equipped with (mixing) shaft and roller in the sizing agent tank, the (mixing) shaft is connected with the driving motor who establishes outside sizing agent tank respectively with the roller, and the roller is established in the top of (mixing) shaft, filling paste in the upper surface of roller and sizing agent tank's the upper end parallel and level, sizing agent tank, and the thick liquid facial height degree of these thick liquids is higher than the lower surface of roller, and the (mixing) shaft submergence is in thick liquids. The utility model discloses utilize the continuous stirring of (mixing) shaft, effectively avoid the thick liquids caking, guarantee going on smoothly of production, prolong sizing agent tank's life.