The invention relates to a wash tank device for a top back washer. The wash tank device comprises a wash tank (1), and is characterized in that four groups of upper pressure rollers (2), lower pressure rollers (3) and wash tank guide rollers (4) are arranged in the wash tank (1), and a semicircular protective cover (5) is arranged outside each upper pressure roller (2); and a photoelectric switch (6) is arranged at one side of the upper pressure roller (2). The four groups of upper pressure rollers, lower pressure rollers and wash tank pressure rollers are arranged in the wash tank, and the semicircular protective cover is arranged outside each upper pressure roller, so that the wash tank device for the top back washer has the advantages of higher cleaning efficiency and higher safety factor.