The 85cm telescope is a well-operated prime focus system with high science outputs at the Xing-long station. Using unconventional data obtained on May 12, 2019, super-sky flats in B, V, R, and I bands are constructed and compared to their corresponding sky flats. It is found that typical flat-fielding errors using sky flats are 0.5% for the four bands, but the maximum errors can reach 1.5%--2.0%. Fringing pattern with super-sky flat is also constructed for I band data and publicly available to the community.