Sorghum seedlings of ‘longza 19’ were inoculated with Rhizoctonia solani AG1IA. We investigated the growth and physiological and metabolic indexes of sorghum seedlings at different infection times through pot experiment, so as to reveal the effects of R. solani infection on sorghum growth, osmotic regulatory substances and antioxidant enzyme activities. The results showed that: (1) the plant height, root length, aboveground (stem and leaf) fresh and dry mass, underground (root) fresh and dry mass of sorghum seedlings decreased with the extension of inoculation time, which decreased by 41.0%, 29.2%, 50.0%, 50.0%, 53.3% and 50.0%, respectively compared with the control at 72 h after inoculation. (2) The chlorophyll a content of seedling leaves decreased significantly by 45.3% compared with the control 72 h after inoculation, and the maximum photochemical efficiency (F_v/F_m) of PSⅡ decreased gradually with the increase of inoculation time. (3) The contents of MDA and O₂^-· and H₂O₂ in seedling leaves increased gradually with the increase of inoculation time, and increased significantly by 244.6%, 140.4% and 137.0% compared with the control 72 h after inoculation; The activities of SOD, POD, APX and CAT in leaves changed differently after inoculation, but increased significantly by 16.5%, 60.3%, 50.0% and 36.5% compared with the control at 72 h. (4) The contents of soluble protein and soluble sugar in seedling leaves increased gradually with the increase of inoculation time, and reached a significant level at 24-72 h; It was found that inoculation with R. solani could cause disease spots in sorghum seedlings, excessive accumulation of reactive oxygen species and significant oxidative damage to membrane; In the early stage of infection, sorghum plants mainly accumulate more osmoregulation substances to resist the damage caused by R. solani. In the later stage of infection, the damage is aggravated with the plant, and the activities of antioxidant enzymes are significantly enhanced, so as to maintain the steadystate balance of reactive oxygen species metabolism in sorghum and reduce the further oxidative damage of plant membrane.