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Forest ecosystems on China's Loess Plateau are receiving increasing attention because of their special importance in carbon fixation and conservation of soil and water in the region. Soil respiration was investigated in Platycladus orientalis forest stands of the region at diurnal and seasonal scales. The daily and seasonal average values of soil respiration were 2.53 μmol.m-2.s-1 and 3.78 μmol.m-2.s-1, respectively. On a diurnal and seasonal scale, the variations of soil respiration in the P. orientalis forest show a one-peak pattern. The diurnal dynamics of soil respiration were mainly driven by soil temperature. However, the relationship between soil respiration and soil temperature was not significant, mainly because of the hysteresis effect of soil respiration on soil temperature. Soil moisture plays another dominant role in the ecosystem carbon balance, but was not affected by soil temperature in P. orientalis forest on the semiarid Loess Plateau.