Abstract: In order to increase the utilization rate of shiitake mushroom by-products, the shiitake mushroom stem was crushed after superfine grinding with a jet mill, with coarse powder and 40 mesh powder as the control. The effect of jet milling on the physicochemical properties of shiitake mushroom stem powder and the dissolution amount of functional components represented by ergosterol and polysaccharides were studied. The cumulative dissolution rate of ergosterol and polysaccharides was fitted by the Weibull model. The results showed that after superfine grinding by jet milling, the average particle size (D₅₀) of powder decreased to 3.21 μm, bulk density, tap density and L^* value increased from 0.15 g/mL to 0.25 g/mL, 0.23 g/mL to 0.42 g/mL, 65.31 to 73.49, respectively. The superfine powder fluidity, water holding capacity and swelling capacity were significantly enhanced (P<0.05). The cumulative dissolution 50% of the time (T₅₀) of ergosterol and polysaccharide in superfine powder was reduced by 2.56 min and 8.14 min, respectively, compared with coarse powder. And cumulative dissolution rate at 45 min (Q₄₅) increased by 10.88% and 19.15%, respectively. The powder properties and the dissolution rate of the functional ingredients were improved, after the jet milling to treat the shiitake mushroom stem, which was conducive to the comprehensive utilization of shiitake mushroom by-products.