Abstract: In order to determine the effect of Trichoderma on plant growth and salt dissolution, Trichoderma longibranchiatum was selected as the research object to determine its effects on rice biomass, physiological and biochemical indicators and photosynthetic indicators under saline-alkali stress. The results showed that the seed germination potential of rice increased 25%-32% and the germination rate increased 0.03-0.20 compared with uninoculated fungi. After 7 days’ treatment, both the radicle and germ of rice were significantly elevated between 38.9%-50% and 14.2%-50%. In terms of biomass, Trichoderma longibranchiatum increased the plant height, the fresh and dry weight of the aboveground and underground parts, and the root length of rice seedlings under saline-alkali stress. The underground dry weight significantly increased, which was 15.3%-42%. Chlorophyll a increased 16.5%-27.1%, chlorophyll b increased 19%-29.5%, and total chlorophyll increased 19.7%-19.9%. In terms of physiological indicators, peroxidase, catalase and superoxide dismutase, MDA contents decreased after inoculation under saline-alkali stress. Peroxidase significantly decreased 27.9% under alkaline conditions. In terms of photosynthetic indicators, Trichoderma longibranchiatum increased the photosynthetic rate, transpiration rate, stomatal conductance, and intercellular CO₂ concentration of rice leaves. The results showed that Trichoderma longibranchiatum promoted the growth of rice seedlings under saline-alkali conditions.