Abstract: 1, The constitution of subalpine dark coniferous forests in Xizang is chiefly of single superior structure or confluent structure of Picea (Spruce) and Abies (Fir). In regions of distribution, there are more pure forests of Picea in the lower parts of shady slopes, and at the higher altitudes there are more pure forests of Abies. On shiny slopes, there are more forests of mixed Picea, Abies and Ouercus aquifolioides at the lower altitudes, and on the higher parts there are more forests of mixed Abies, Picea and Sabina tibetica, with pure sabina saltuoria forests on top of them.2, The forests of Picea and Abies are all irregular forests and the pure forests of Sabina are more regular forests. The synusiae under the subalpine dark coniferous forests are intact and complete, with l-2 of them well developed. Many well developed Actinothuidium (Mogs) synusiae are found in the lower parts of shady slopes and many underplants of Rhododendron of sub-arboreous are found at the higher altitudes. In the lower parts of shiny slopes, underplants of Sinarundinaria (Chinacane) often occur. Generally, layers of grassland vegetation are undeveloped, but plants out of this story grow well.3, The standing trees of the subalpine dark coniferous forests have a large age-scope, the principal plants being more than 200-300 years old and the urulsrplants about 100 years old. The standing trees of the dark coniferous forests have longevity and continue to grow after an age of 200-300 years, and the trees of under stories even show a potential superiority of growth.4, The trees of the subalpine dark coniferous forests have a wide range of dia-meter grades and the heights of the trees also vary greatly. Where the conditions of locality are good, the trees often have breast height diameters of about 60-100 cm and heights of about 40-50 m, with the tallest ones reaching over 70 m. The patterns of the variations of the tree tallness and the amount of wood stock of the forest are as follows: humid region > semi-humid region; shady slope > shiny slope; low elevation > high elevation (distributed region); Picea forest > Abies forest> osabina saltuoria; Actinothuidium forest types > brush forest types> sinarundinario.