As exposed to the air, plant leaves are sensitive to the changes in environments. In this study, we investigated the leaf anatomical characteristics and their correlations with environmental variables for 66 dominant species of grasslands in the Tibetan Plateau. The results showed that: (1) Plants of grasslands on the Tibetan Plateau showed typical characteristics to adapt to the alpine environments, such as thicker epidermal and mesophyll layers than plants in other areas. In detail, epidermal cells of some plants can be differentiated into special structures such as blister cells and epidermal hair; mesophyll cells had thick cell walls, dense cytoplasm with rich reserves, containing large volume and amount of chloroplasts. Besides, the thick palisade tissue was composed of multi-layers of tightly arranged small-volume cells. The spongy tissue was composed of relative small cells, with large intercellular space, however, its thickness varied greatly among species. Most of the plants had well-developed aerenchymas and sclerenchymas in the mesophyll cells, with the advanced sclerenchymas around the veins and vascular bundles often extending to the leaf surface. Many vascular bundle sheaths and idioblasts (reserve cells) were observed within the mesophyll cells. For most plants, these idioblasts existed in (or around) the vascular tissues; furthermore, the idioblasts existed in one or two cell layers of palisade tissue near upper epidermis for over half of the plants. (2) Thickness of leaf anatomical structures varied in different degrees; in particular, thickness of spongy tissue exhibited the greatest variation (0.34), followed by that of upper epidermal cuticle (0.33), lower epidermis (0.28), lower epidermal cuticle (0.26), upper epidermis (0.26), palisade tissue (0.25) and the leaf as whole (0.17). (3) Thicknesses of leaf anatomical structures were negatively correlated with altitude, thicknesses of all anatomical structures except the upper cuticle were positively correlated with precipitation for growing season; thicknesses of all leaf anatomical structures except the lower cuticle were positively correlated with mean temperature for growing season. These results suggested that different components of the leaf were relatively thin at high altitudes, and the leaf was relatively thick in the areas with high precipitation and mean temperature for growing season.