The changing trends in foodgrain and oilseed production, and the affecting factors of that trends are analyzed in this paper. It is shown that the per unit yield is the predominant driving force of foodgrain and oilseed production in Tibet. Sustainable increase of the per unit yield of foodgrain and oilseed production, and following countermeasures should be adopted: application of improved crop varieties, promotion of the cultivation system, improvement of the low yield land and building up of the capacity for irrigation system for cultivated land.