<p>Soil salinization seriously threatens the health of existing farmland and crops, and peanut cultivation is also threatened by soil salinization. Biochar has been widely studied as a soil amendment to improve the growth of various crops such as wheat and corn in saline alkali land, yet its effects on peanut growth in saline alkali soils remain underexplored. Therefore, we aim to conduct greenhouse pot experiments to test the promoting effect of biochar on the growth of peanuts in saline alkali soil, and to study the impact mechanism of biochar microbial composition. The results indicate that the application of biochar can directly improve the physicochemical properties of peanut rhizosphere soil. Compared with the control group, peanut sprout height and fresh weight significantly increased. The exploration of its causes has found that biochar can directly or indirectly improve the properties of rhizosphere soil, including reducing soil salinity and alkalinity, and increasing water content. On the other hand, biochar treatment significantly increased the availability of essential nutrients like ammonium nitrogen, available phosphorus, and organic matter which is crucial for maintaining peanut growth. At the same time, the content of stress resistant substances, including peroxidase activity, in peanuts significantly increased, while the content of malondialdehyde also decreased, further indicating that the application of biochar promotes the resistance of peanuts to salt alkali stress. In summary, the application of biochar can directly reduce the pH and moisture content of peanut rhizosphere soil, increase rhizosphere nutrient content, and enhance peanut antioxidant enzyme activity, ultimately promoting its growth in saline alkali soil.</p>