Studying the relationship of the transpiration rate (Tr) of plants with leaf traits is important for understanding the adaptability of plant leaf function in heterogeneous habitats. The study aimed to explore the relationship of transpiration rate with leaf traits in different slopes. The study site was located in a degraded alpine grassland on the eastern Qilian Mountains, Gansu Province, China (101°32'34'-101°33'50"E, 38°36'1'2'-38°17'N). The study area is selected which contains four standard slopes and is a relatively independent hill. The test method is as follows, first, the mountain is divided by four slopes in the topography. Second, along the four slopes every 30 m set a sample area (1 m×1 m) from the bottom to the top of the mountain elevation, each direction is 8 pieces, a total of 32 samples. Third, choose 6 plants from each samples, total 48 plants of each direction. The results showed that with the slopes turned from north to south, the height, coverage, density, and soil moisture of the grassland community gradually reduced, the height, leaf area (LA), Tr, stomatal conductance, and net photosynthetic rate of Thermopsis lanceolate decreased, and the leaf thickness increased. There was a highly significant positive correlation (P < 0.01) between Tr and LA, and significant negative correlation (P < 0.01) between Tr and leaf thickness on the northern and southern slopes, whereas significant positive correlation (P < 0.05) between Tr and LA or between Tr and leaf thickness was found on the eastern and western slopes. Thermopsis lanceolate build up a small and thick leaves to realise low transpiration rate in the southern slope, in the northern slope, Thermopsis lanceolate select a large and thin blades to achieve low transpiration rate. It reflects the plant survival strategy through leaf biomass allocation mechanism to realize the effective utilization of resources in heterogeneous habitat.