In this study, the linear regression between soil respiration rate and root biomass was adopted to estimate the contribution of root respiration to total soil respiration in Puccinellia tenuiflora dominated community of a semi-arid meadow steppe in northeast China. The soil respiration rate reached the maximum value 2.45μmol·m-2·s-1 in late June and the minimum value 0.39 μmol·m-2·s-1 in late September. Soil temperature is the major environmental factor controlling the seasonal variation of soil respiration. The root biomass ranged from 0.54 to 0.97 kg·m-2, showing insignificant seasonal variation. Microbial biomass C reached the maximum value 0.50 g·m-2 in mid August, presenting the least within- site variation. The pattern of seasonal change in root respiration rate was different from that in microbial respiration. Root respiration rate ranged from 0.19 μmol·m-2·s-1 in May, to the maximum value 1.39μmol·m-2·s-1 in late June, then down to 0.28 μmol·m-2·s-1 in late September; whereas, microbial respiration rate ranged from 0.61 μmol·m-2·s-1 in May, to the maximum value 1.27 μmol·m-2·s-1 in July, then down to 0.11 μmol·m-2·s-1 in late Sep- tember. There was a significant exponential correla- tion between microbial respiration rate and soil tem- perature, whereas not so for root respiration rate. We estimated that the contribution of root respiration to total soil respiration ranged within 24%-57% in spring and summer, and increased to 73% in autumn.