<p>Anthropogenic activities have increased phosphorus (P) inputs to wetland ecosystems, potentially altering nutrient cycling and greenhouse gas dynamics. However, the effects of P enrichment on methane (CH₄) emissions in alpine wetland systems, particularly on the Qinghai-Tibet Plateau (QTP), remain poorly understood. Here, we conducted a 2-year field experiment with graded P additions—low-P (LP, 5&#xa0;kg·ha^− 1·a^− 1), medium-P (MP, 10&#xa0;kg·ha^− 1·a^− 1), high-P (HP, 15&#xa0;kg·ha^− 1·a^− 1)—and a control (CK) to assess CH₄ flux during the growing season (May–October). Using opaque static chambers and gas chromatography, we quantified CH₄ emissions alongside key soil environmental parameters and microbial community structures. Results showed that P addition significantly increased CH₄ emissions from the Gahai wet meadow, with CH₄ fluxes 3.75–5.21 times higher than in the control. P enrichment also significantly elevated soil organic carbon and total phosphorus content (<i>P</i> &lt; 0.05), increased the relative abundance of <i>Chloroflexi</i>, and reduced <i>Bacteroidete</i>—a microbial shift likely driving enhanced CH₄ emissions. These findings suggest that phosphorus enrichment alters nutrient availability and microbial community composition in alpine wetlands, promoting CH₄ release and exacerbating carbon loss and greenhouse effects in these ecosystems.</p>