Numerical simulation method was introduced to study the micro flow field on the adjacent screen layer (0~10mm in height range) of bionic nonsmooth screen, in which the draught angle and surface feature were chosen as factors. Bionic nonsmooth rape cleaning screen was made to compare with the common smooth screen in the field. The result showed that the draught angle basically had no influence on the micro flow field on the adjacent screen layer. The bionic feature would destruct the little vortex among the holes into two smaller vortexes which reduced the contact possibility between tiny rape materials and cleaning screen and lowered the adhesion degree. The result also showed that the bionic convex surface could lower adhesion better than bionic concave surface.