Based on the long-term fertilization experiment in the arid upland fields on the Loess Plateau that started in 1984, soil respiration, soil temperature and soil moisture in the 0—10cm soil layer of winter wheat fields different in fertilization during the summer fallow season (from July to September) were monitored with the dynamic closed chamber method (LI-8100 USA), and dynamics of soil respiration and its relationships with environmental factors were investigated. Results show that soil respiration varied drastically within the range from 5.05μmol m^-2 s^-1 to 0.06 μmol m^-2 s^-1 with a variation coefficient of 116.5% and a mean of 2.00μmol m^-2 s^-1. For the whole study period, in terms of soil respiration, the treatments followed a decreasing order of NPM > M > NP > N and CK, with cumulative CO₂- C emission being 2.0, 1.6, 1.2, 0.8 and 0.8 Mg ha^-1, respectively. The relationship between soil respiration and soil moisture appeared in an extremely significant parabolic curve (p<0.01), which explains 55% of the variation of the soil respiration. Although soil respiration was in extremely significant linear relationship with soil temperature (p<0.01)，soil temperature could explain only 19% to 39% of the variation of soil respiration. Strength of the response of soil respiration to ploughing significantly (p<0.05) was positively related to soil microbial biomass carbon and soil organic carbon showing a linear relationship, but not to total nitrogen or soil dissolved organic carbon (p> 0.05); the effects of rainfall on soil respiration depended on soil moisture before a rainfall event. In soils deficient in soil moisture for long, rainfall significantly stimulated soil respiration, while in soils sufficient in soil moisture, rainfall inhibited soil respiration. Magnitude of the effect is closely related to soil organic carbon, total N, soil soluble carbon and soil microbial biomass carbon. Soil respiration during the fallow season may be affected by soil moisture, alteration of wet and dry, soil temperature, rainfall, ploughing, and soil organic carbon level.