Abstract:The prebreak of common wheat with medium gluten was conducted with a roller mill.The roll clearance was adjusted to obtain different prebreak releases，and the effects of different roll clearances of prebreak on the impurities on the wheat surface，flour yield，and flour quality were studied.The results showed that with the decrease in prebreak roll clearance，the prebreak release increased significantly.As the prebreak roll clearance decreased within a certain range，the test weight，deoxynivalenol，aerobic plate count，molds and yeasts，and coliforms on the surface of wheat decreased significantly.After prebreak，the moisture content and whiteness of the screened fine materials increased gradually，and the ash content，deoxynivalenol，aerobic plate count，molds and yeasts，and coliforms decreased gradually，which indicated that the prebreak had cleaning effect on wheat grain.Compared with the wheat without prebreak，the proportion of large bran pieces，the total flour yield，and flour whiteness first increased and then decreased as the roll clearance decreased，while the ash content of wheat flour first decreased and then increased.Furthermore，the wet gluten content increased，and the damaged starch content decreased.Setting the rolling clearance at 2.4 mm in the prebreak can improve both the yield and the quality of wheat flour.