Abstract: Tempering is an indispensable process before wheat grinding, which can effectively improve the milling effect and quality of wheat flour. In this paper, the effects of tempering on the granule size distribution and its composition of wheat flour were investigated by changing the water content (14.5%, 15.5%, 16.5%), temperature (25, 35, 45 ℃) and way of tempering (vacuum conditioning, conventional conditioning). The results showed that with the increase of tempered water, the granule size of wheat flour first became fine and then coarse, the yield, ash, total protein, glutenin and damaged starch decreased, L* and gliadin increased, and the total starch decreased first and then increased.After increasing the tempering temperature, granule size, total starch and amylopectin of wheat flour increased gradually, while the total protein, glutenin and damaged starch decreased gradually. Compared with conventional conditioning, vacuum-conditioned wheat flour had larger overall granule size, lower content of gliadin and damaged starch, and higher content of glutenin and amylopectin. The quality of wheat flour was significantly different under different tempering conditions. When the tempering moisture and the temperature were 15.5% and 25 ℃, the granule size of wheat flour had the highest fineness, higher yield, lower ash content and better quality.