Studying the relationship between plant diversity and biomass of typical plantations in the alpine region of Qinghai contributes to the mutual prediction of plant diversity and biomass. It is of great significance for elucidating the role of plant diversity in ecosystems. We selected the typical plantations in the alpine region of Qinghai as the research object. The plant diversity and ground biomass of the arbor, shrub and herb layers of the plantations were quantitatively studied by standard land survey method, biomass model estimation method, and biomass harvesting method. The results showed that:(1) the plant diversity of the herbaceous layer in the artificial forests was higher than that in the shrub and arbor layers. Community plant diversity was greatly affected by plant diversity of herbaceous layers. (2) The ground biomass of plantations with a forest age of 20 years was from 921.9532 g/m² to 6314.9671 g/m², and that with a forest age of 35 years was from 9563.0731 g/m² to 15181.1201 g/m². There was a significant difference in ground biomass between different forest types. (3) The proportion of ground biomass in the shrub layer and herb layer of the artificial forest in Qinghai Province was small, ranging from 0.77% to 1.49% and from 0.004% to 18.54%, respectively. The ground biomass of the arbor layer dominated the total biomass of the ground part of the community. (4) There was a cubic functional relationship between herbaceous ground biomass and community and herbaceous plant richness in the artificial forests of Qinghai high-altitude area (P<0.05).