Abstract: Studying the response of soil microbial community structure to simulate warming is of great significance for predicting soil carbon, nitrogen and phosphorus cycles in the context of global climate change. Therefore, the effect of simulated warming on the soil microbial community structure was studied with the open-top chamber (OTC), as determined by phospholipid fatty acids (PLFAs) in the alpine timberline ecosystem in western Sichuan. The results showed that simulated warming enhanced the daily mean air temperature by 0.87 ℃, the daily mean temperature of soil organic layer (OL) and mineral soil layer (ML) increased 0.5 ℃ and 0.23 ℃, respectively. The microbial community composition of soil organic layer was more sensitive to the simulated warming than that of the mineral soil layer. Bacteria (TB) were more sensitive to the simulated warming than fungi (TF). Simulated warming also significantly affected the ratios of fungi to bacteria (F/B) and gram-negative bacteria to Gram-positive bacteria (G^-/G⁺) of the soil organic layer, whereas it had no significant effect on the microbial PLFAs content of mineral soil layer. In all treatments, the content of microbial PLFAs and the ratios of F/B and G^-/G⁺ were in order of non-growing season (NGS) < early growing season (EGS) < late growing season (LGS). The redundancy analysis suggested that the soil carbon contents (DOC 12.1%, DC 9.5% and TC 3%) were the determination factors affecting microbial community structure, and the dissolved nutrient (DOC and DC) had a greater effect on microbial community structure than the total nutrient (TC and TN).