Abstract: The model based on relations between net photosynthesis of Changbai larch （Larix olgensis）seedlings and temperature, CO2 concentration and other factors has been constructed. This model simulates the daily process of net photosynthesis and dry matter accumulation of Changbai larch seedlings in the growing season under controlled environment, and predicts the possible change of dry matter accumulation under changed temperature and CO2 concentration.