Abstract: Inspired from the comparatively mature technology of soil moisture conservation, developing in the semi-arid and arid region in China, the authors proposed the new concept of "Soil Moisture Conserving Irrigation(SMCI)", which may play a role, just like casting a brick to attract jade, in widening relevant research on water-saving irrigation and the development of water-saving undertaking of China. At the same time, through the plot experiment, the effect of the straw mulch on the field environment was studied. Result indicates soil water content with straw covered is obviously higher than contrast in 0~50 cm depth of soil Variation of temperature in one day inclined to moderation after straw mulching, the lowest range of temperature per day is 12.43℃, compared to 50.03℃. Topsoil soil bacterium, actinomyces, and fungi after straw mulching are 1.63 times, 1.68 times and 1.07 times as much as those of the contrast. The indexes of height, diameter and leaf area are obviously greater than those of the contrast, in the same treatment, the photosynthesis rate, transpiration rate of maize are all greater than those of the contrast, but the water use efficiency of single leaf is nearly the same between treatment and contrast. The yield of the treatment increased at the percent of 22.16%, 20.28% and 12.75%, and increased with the rise of quantity of irrigation water.