Variations in precipitation had a significant impact on the alpine meadow ecosystem. Among plant leaf traits, leaf vein properties are very sensitive to the changed precipitation. However, how the leaf traits of alpine plants respond to precipitation variations was still little known. The precipitation in the study area was artificially regulated increase and decrease of rain using rainwater shed, and the responses of leaf properties from 8 main plants in the alpine meadow were systematically analyzed under 50%, 100%, and 150% rainfall treatments. This study investigated the effects of altered precipitation on the vein mass per leaf mass (VMM), vein length per area (VLA), leaf size (LS), leaf mass per area (LMA), total organic carbon concentration (TOC), total nitrogen concentration (TN), carbon isotope discrimination (δ¹³C) and the ratio of carbon to nitrogen (C/N). The results indicated that water increasing significantly enhanced LS, δ¹³C, TOC, and TN, but significantly reduced for VLA. While water decreasing significantly reduced the LS and δ¹³C. There were synergistic changes and mutual constraints in the response of plant leaf traits to precipitation alteration. Plants belonging to different water ecological groups had different responses to precipitation alteration. Mesophytes actively responded to the increase in precipitation by increasing LS and reducing VLA. The LS of Kobresia humilis was increased by 200.3%, and the VLA was reduced by 17.5%. While dry mesophytes responded to the decrease in precipitation by reducing LS and increasing VLA. The LS of Elymus nutans and Stipa purpure decreased by 54.9% and 30.7%, and their VLA increased by 25% and 22.4%, respectively. Pinnate vein plants could enhance VLA and δ¹³C in order to adapt to water increasing condition. The VLA of Medicago ruthenica and Gueldenstaedtia diversifolia increased by 7.8% and 4.0%, and the δ¹³C increased by 2.5% and 3.3%. While for parallel vein plants, they remained unchang or decrease. Water reducing enhanced VLA of parallel veins plant and reduced δ¹³C, while had no impact on pinnate vein plants. The VLA of S. purpure increased by 22.4% and the δ¹³C decreased by 2.9%. The plant leaf traits were much more significantly sensible to water increasing than water reducing, and the effect of water increasing was about 2 times than that of water reduction. LS was the most significantly sensitive among all leaf traits, about 10 times that of other leaf traits. Therefore, plant morphology plasticity played a prominent role when responding to short-term precipitation variation. Enlarging or reducing leaf size was the most effective way to respond to precipitation alteration. However, plant plasticity was significantly different among the water ecological types and leaf vein types.