The energy flow process between litter of Puccinellia tenuiflora community and soil microorganisms has been studied and a compartment model established to discuss the characteristics and function of microorganism during decomposing litter. The results show that during the process of energy flow through microorganism, the energy input is 1357.84 kJ@ m-2@a-1; the energy absorbed by microorganism is 733.97 kJ@ m-2@ a-1, in which up to 552. 29 kJ@m 2. a-1 energy is consumed for respiration and the energy about 181.23 kJ@ m-2@ a-1 is formed for microorganism biomass. 95 % of the litter accumulated on the ground annually would be decomposed in 1.85 years and the decomposition index is 1.93. The mathematical model of the energy x 1 ( t ) absorbed by microorganism of the year was described as x1(t) = 733.97 - 0.82e 1.85t and the model of the energy x2(t) formed for microorganism biomass of the year is expressed as x2 (t) ＝ 181.23 - 0.37e-1.85t + 0.005e- 4.0st. The equilibrium state of the energy absorbed by microorganism is 733.97 kJ@m-2@a-1 and the equilibrium state of the energy formed for microorganism biomass is 181.23 kJ@m-2@a-1.