Abstract: The calorific values of plants is an important index in the research of energy flow of the grassland ecosystem. The measurement of calorific values uses bomb calorimeter. The principle is to burnout quantitative sample in a bomb with oxygen and the calorific values of plant material is calculated according to raised temperature value. The exact data would be obtained by paying attention to keep temperature values accuratly, mix sample evenly, select the optimum pressure of oxygen and reducing sample pollution as much as possible. The results have shown that calorific values of grassland plants varies along with different species of plants and different parts of plant in the same species and different growing stages of plant.