Abstract: To investigate the contents of main constituents in the aqueous extract of Astragalus and their effect on the mycelium growth of Pleurotus ostreatus, Lentinus edodes, Auricularia auricula, Pleurotus nebrodensis and Pleurotus eryngii, the contents of total saponins, total flavonoids, total phenolic acids and total polysaccharides in the aqueous extract of Astragalus were determined using ultraviolet spectrophotometry, and the contents of calycosin-7-O-β -D-glucoside and fomononetin-7-O-glucoside in the extract were analyzed using high performance liquid chromatography. The results showed that the aqueous extract of Astragalus contained calycosin- 7- O-β - D- glucoside and fomononetin- 7- O- glucoside. The content of total saponins, total flavonoids, total phenolic acids and total polysaccharides in the extract was 62.67 mg/g, 56.48 mg/g,12.19 mg/g and 564.26 mg/g, respectively. Within the concentration range of test, the mycelium growth of Lentinus edodes was suppressed by Astragalus aqueous extract. For Pleurotus ostreatus, Auricularia auricula, Pleurotus nebrodensis and Pleurotus eryngii, the mycelium growth was promoted when the concentration of the extract was lower than certain thresholds, and was obviously inhibited when the concentration of the extract was above those thresholds. Pleurotus eryngii showed the highest mycelium growth inhibition threshold value, it was 1.5 g/100 mL. The main constituents of the aqueous extract of Astragalus were polysaccharides, saponins and flavonoids. At low concentrations, the extract promoted the mycelium growth of the tested edible fungi, whereas at high concentrations, it inhibited the mycelium growth.