In order to explore the variation characteristics of the three phase composition of soil "solid-liquid-gas" in alpine meadow at different altitudes and slope aspects, the alpine meadow in eastern Qilian Mountain was taken as the research object, and the vegetation characteristics and soil physical characteristics of alpine meadow at the different altitudes (2 800, 3 000, 3 200, 3 400, 3 600, 3 800 and 4 000 m) and aspects (sun slope, shady slope) were analyzed. Combined with vegetation index fitting, the optimal composition ratio of the "solid-liquid-gas" three phase of alpine meadow was explored. The results showed that the vegetation coverage, grass layer height and aboveground biomass increased first and then decreased with the increasing of altitude, and reached the maximum at 3 200 m. At the same altitude, the vegetation coverage, grass layer height and aboveground biomass on the shady slope were higher than those on the sunny slope. The variation law of soil bulk density with altitude and slope aspect was opposite to that of vegetation coverage, while the variation laws of soil water content, porosity and water holding capacity were similar to that of vegetation coverage. After equation fitting, the productivity of the alpine meadow was the best when the soil "solid-liquid-gas" three phase ratio was 31:33:36. In conclusion, 3 200 m was the central typical area of the distribution of alpine meadow in the eastern Qilian Mountains. The altitude and slope aspect were important environmental factors affecting the soil physical quality of the alpine meadow and the "solid-liquid-gas" three-phase composition. The optimum ratio of "solid-liquid-gas" in meadow soil in this area was 31:33:36.