Abstract: Six species of pines are distributed in Xizang. They are: Pinus griffithii McClell., P. armandi Franch. and P. gerardiana Wall. of haploxylon pines and P. densata Mast., P. yttnnanensis French. and P. roxburghii Sarg. of diploxylon pines. According to the relation of these pines with water-temperature conditions, 4 ecological types may be divided: the warm-temp erate and wet type (P. griffithii), the warm-temperate and dry type (P. yunnanensis, P. roxburghii), the temperate-cold and moist type (P. armandi) and the temperate-cold and dry type (P. densata). The composition and structure of every pine community reflect the ecological environments of the given pine in the region. The main pine comnmnity in Xizang are P. griffithii forest and P. densata forest. The P. griffithii forest is distributed on the southern side of Himalayas, while the P. densata forest on the northern side of Himalayas and the southern part of Hengtuan mountains. This indicates that the Himalaya range is a clear boundary and there is difference in water-temperature condition between southern and northern parts. They belong different vegetation regions. The different distribution of other several pine forests reflects the difference of environmental conditions within these two regions. These facts have significance in the investigation of the regularity of vegetation distribution and vegetation division in Xizang. Besides, the vertical distribution of pines cannot be used as a marker to divide the altitudinal belts due to the wide range of adaptation of pines, though there must be regularity of vertical distribution too.