Based on the water level decline simulation control experimental platform in the Naleqiao Marsh of the Ruoergai Plateau, this study investigates the response of stomatal characteristics and photosynthetic traits of Carex muliensis in the alpine marsh wetland of Ruoergai to water level decline and explores the correlation between these traits. The results indicate that following a decline in water levels, the stomatal number, stomatal density, net photosynthetic rate, transpiration rate, stomatal conductance, and chlorophyll content of Carex muliensis significantly decreased. In contrast, stomatal area, leaf thickness, and intercellular CO2 concentration significantly increased. There were no significant differences in the vascular bundle area, vessel area, and sieve tube area. The correlation between stomatal characteristics and photosynthetic traits was strong, while anatomical traits did not show a significant correlation with either stomatal or photosynthetic traits. However, there were strong internal correlations among stomatal traits, anatomical traits, and photosynthetic traits. There is a certain degree of coordinated variation between stomatal traits and photosynthetic traits, although this coordination does not exist under all water level conditions. Additionally, Carex muliensis exhibits a "rapid investment-return" resource utilization strategy. Overall, the study demonstrates the high plasticity of Carex muliensis in adapting to low water levels. The relationship between stomatal characteristics and photosynthetic traits fully reflects the trade-off strategy of Carex muliensis, showcasing the adaptive strategies of leaf structure and function to water level changes in the alpine wetland plants of the Ruoergai Plateau, which helps them survive and reproduce in changing environments.