Abstract: This study determined effects of different mulching materials and methods on soil water, soil temperature, grain yield (GY) and important agronomic parameters of spring wheat in a semi-arid rain fed area of northwestern China. A total of 8 mulching treatments were tested in this study. These included straw mulching, plastic film mulching such as flatten culture and whole mulching, micro-ridge and whole mulching, large ridge and half mulching, compared with a non-covered treatment as control (CK). There were significant differences in soil moisture, soil temperature and GY among the various treatments. Compared to the CK, mulching significantly increased GY by 7.7% to 44.9%, with the maximum yield increase occurring in micro-ridge and whole mulched plastic film treatments. The spikes per unit area (SPUA) were the main factor responsible for difference in GY. There was a highly positive correlation (r=0.788^*) between SPUA and GY. Compared to the CK, mulching increased the average soil moisture in the 0-200 cm soil layer during the entire growth period by 0.3%-1.7%, and the highest soil moisture levels were those of micro-ridge and whole mulched white film (C₁) and large ridge and half mulched black film (D₂). Both mulching with wheat straw (A₁) and large ridge and half mulched black film (D₂) decreased average soil temperature in the 0-25 cm soil layer during entire growth period by 1.4 and 0.9℃, while soil temperatures of the other 6 mulching treatments were increased by 0.3-1.8℃. The maximum warming occurred in flatten culture and whole mulched white film (B₁) treatments. However, more detailed analysis of spatio-temporal differences in soil temperature and soil moisture revealed that the various treatment effects were most strongly seen in different soil layers or in different growth periods. Soil moisture data were recorded at 48 time points in each treatment. Each mulching treatment had 26-40 points with soil moisture higher than the CK, and 8-22 points lower than the CK. During the entire growth period, mulching predominantly increased soil moisture at the flower-filling stage, and decreased soil moisture in the booting stage. Mulching-induced soil moisture increases were most evident in the 20-40 cm soil layer, and mulching tended to decrease moisture in the 60-90 cm soil layer. Soil temperatures were measured and recorded at 25 time points in each treatment, and each of the mulching treatments varied in numbers of points higher (range 0 to 24 points) or lower (range 1 to 25 points) than CK plots. The maximum warming was observed in the 25 cm soil layer.