Straw mulch has not only a positive effect, but also some negative effects during the seasonal freeze-thaw period. Straw mulch weakens the heat and moisture transfer between the soil and air, and it will go against the crop if the soil temperature rises slowly in the spring. With the aim of revealing the temporal and spatial variation of the soil profile moisture and temperature under different maize straw mulch thicknesses during the seasonal freeze-thaw period, a field experiment was conducted from November in 2005 to March in 2006 at Taigu Water Balance Experimental Field, Bureau of Hydrology and Water Resources Survey of Shanxi Province. Maize straw at rates of 2 100 kg/hm2 (mulching thickness was 5 cm), 4 300 kg/hm2 (mulching thickness was 10 cm), 6 500 kg/hm2 (mulching thickness was 15 cm), 8 600 kg/hm2 (mulching thickness was 20 cm) and 12900 kg/hm2 (mulching thickness was 30 cm) was placed on field plots (JD05 JD10, JD15, JD20, JD30). The soil profile moisture and temperature contours of the bare plot (LD) and five kinds of maize straw mulching thickness plots were compared. The temporal and spatial variation of the soil profile moisture and temperature were analyzed according to a statistical analysis. The results showed that the maximum frozen depth of LD was 52 cm, and the soil profile moisture and temperature of LD varied more dramatically during the seasonal freeze-thaw period and the depth of 0 to 40 cm was an active layer of water and temperature variation (ALWT) and the higher moisture zone (HMZ) appeared at the depth of 20 to 45 cm. However, the maximum frozen depth of JD05 and JD10 was 23 and 10 cm respectively that lagged from LD by about 15 days. For JD05, the depth of 0 to 20 cm was ALWT and HMZ (maximum soil moisture content was 22.5%) appeared at the depth of 15 to 25 cm. For JD10, the depth of 0 to 10 cm was ALWT and HMZ (maximum soil moisture content was 21.3%) appeared at the depth of 5 to 10 cm. Influenced by soil freezing-thawing and maize straw mulching, the effect of soil moisture conservation was best when maize straw mulching thickness was 5 cm, and the soil moisture content of the cultivated layer (from 0 to 20 cm) was 18%to 21%, which was higher than that of other plots. When maize straw mulching thickness was up to 15 cm, the variation of the soil profile moisture and temperature was small and it had the best effect of heat preservation, the soil profile temperature changed relatively stably and the minimum temperature reached 1.1℃. When maize straw mulching thickness exceeded 15 cm, the effect of soil moisture conservation and heat preservation was less obvious with the increasing of maize straw mulching thickness. Therefore, to aim at prevention of frost damage and conservation of soil moisture, the best maize straw mulching thickness is 10 to 15 cm. The research results tend to provide a reference for scientific maize straw mulching on farmland in a seasonal freeze-thaw area during winter and spring.%为了揭示季节性冻融期秸秆覆盖量对土壤剖面水热时空变化的影响，分析对比了裸地和5种不同玉米秸秆覆盖厚度（5、10、15、20和30 cm）地块的土壤剖面含水率和土壤温度等值线变化特征，采用数理统计分析方法对土壤剖面水热变化进行了统计学分析。结果表明：在季节性冻融期，裸地最大冻结深度为52 cm，土壤剖面水热变化较为剧烈，0～40 cm属于水热变化活跃层，覆盖厚度为5和10 cm时的土壤剖面水热变化活跃层分别为0～20和0～10 cm。秸秆覆盖厚度为15 cm时可平抑土壤剖面水热的变化，并能达到良好的保温效果。秸秆覆盖厚度为5 cm时，在土壤冻融作用和秸秆覆盖的双重效应下，耕作层土壤水分较其他地块高，储水保墒效果显著。当秸秆覆盖厚度大于15 cm时，土壤保墒保温效果不随秸秆覆盖量的增加而增强。从预防冻害和蓄水保墒角度出发，最佳秸秆覆盖厚度为10～15 cm。研究成果对于季节性冻土地区冬春季节农田秸秆覆盖的科学实施具有重要的指导意义。
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