Abstract: As a large carbon pool, the shelter forest is an important part in the study on the CO2 fixing efficiency of the forest ecosystem. The soil respiration is a dispensable part of the CO2 fixing efficiency. Nine fast growing poplar in the shelter forest were selected, which all were close to each other and in the similar environment and different age level. The data were collected monthly in the growing season (May to October). The soil temperature and respiration were observed. The analysis results revealed that the most active soil respiration was observed in July and August during the growing season in Yili, Xinjiang. The maximum of soil respiration in the daytime appeared around 16:00. The largest absolute and relative value both could be found in August, the bloom month of plants in Xinjiang. As the growing of the forests, the absolute and relative changing of soil respiration in the daytime and every month were diminished. From the results of estimating, the R2 reaches the peak when comparing the function between the soil temperature (5 cm under the soil surface) and respiration with the Power model.