Surface mulching is a good way to fight drought and conserve water for agricultural production.The paper is studied by the method of field experiment.in typical semi-arid area. The experiment was localed on the field of Wuchuan County Dry Farming Station in Inner Mongolia province from 2004 to 2005. Six treatments included: non-mulching (control), plastic film mulching, single-straw mulching in spring, double-straw mulching in spring, single-straw mulching in winter, double-straw mulching in winter. Two plants were potato and corn. Based on 1 year field experiment, the effects of surface mulching on the soil was studied and analyzed systemically. The main results included: 1. Surface mulching could reduced soil evaporation and maintain higher soil water content by avoiding soil water losses. The effect of straw mulching was more obvious. 2. The effect of different surface mulching treatments to topsoil temperature appeared: surface mulching could preserve and increase soil temperature in the period of low-temperature, straw mulching had "cryogenic effect" to stabilize geothermal changes in the period of high-temperature. 3. The statistic results of soil nutriments showed: (1) Different treatments of surface mulching obviously decreased the content of soil organic matter. It was different to some proyed conclusions. It should be verified in more years of experiment. (2) The content of soil total N showed no significant difference. But the difference was significant among treatments. (3) Different treatments of surface mulching increased or decreased the content of available P, and it did not show the obviously trend of increasing. There was not significant difference among treatments. (4) Non-mulching obviously decreased soil available K while other various surface mulching increased. Double-straw mulching was more benefit for reinforcing the available K rapidly. 4. The crop yield showed a little trend of increasing, but the difference was not distinct between various treatments.