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Soil respiration was measured with the enclosed chamber method during 2 years in fenced Leymus chinensis steppe, Inner Mongolia, China. Soil water content at 0-10 cm depth was a major limited factor of soil respiration in semi-arid grassland, accounting for 76.4% of the variation. The temperature-dependent exponential function could only explain 38.7% of the variation in soil respiration. With 246 data over the entire experimental period, multiple linear stepwise regressions of soil respiration rate were analyzed with the influencing factors, including soil water content at 0-10 cm depth, air temperature, air pressure, air humidity, total radiation and their interactions. With soil water content at 0-10 cm depth (M and air temperature (Th) as combined factors, the twice linear regression (F = 1.68W7(h) - 109.09) was simple and its coefficients were significant, accounting for 83.1% of the variation in soil respiration. Due to the lack of long-term and continuous soil water content, a water sub-model based on precipitation and evapotranspiration was introduced, which could provide better fits with the measured values (RI = 0.813). The magnitudes of soil respiration calculated from the twice linear regression equation and water sub-model were 439.58 and 463.06 g CO2 m(-2) in 2001 (19 June-23 September) and in 2002 (1 June-24 September), respectively. The mean hourly soil respiration rates were in the range of the previous studies in the adjacent region and the world’s major temperate grasslands. (c) 2006 Elsevier B.V All rights reserved.