Extreme arid climate plays a critical role in affecting farmland hydrological process and crop yield in semiarid rainfed agricultural area. However, relevant field studies on this issue are not enough documented and the related solution to this issue is so far not well defined. Since 1990s, micro-field rain-harvesting farming technology has been developed and extended to a large area in semiarid Loess Plateau of northwest China, however, its functional role as a solution to cope with extreme climate change is not well recognized. In this study, we designed a two-year field experiment to address the issues of field water productivity and hydrological processes by applying ridge and furrow system under the condition of extreme weather. Oat cultivar, Bayou 3 was used as research material in this study. Field experiment was conducted at the Arid Meteorology and Ecological Experimental Station, Lanzhou Institute of Arid Meteorology of China Meteorological Administration (Dingxi County, Gansu Province) in both years of 2010 and 2011, respectively. Five farming treatments including micro-field rain-harvesting mulching technology were designed as follows: control with full irrigation, flat planting, furrow and ridge without mulching planting, furrow and ridge with film mulching planting and bare field without irrigation, respectively. Some critical parameters were systematically measured and recorded including rainfall amount, soil moisture in 0-140cm soil profile, crop growth and yield formation during whole growth period. Least significant difference (LSD) was used to detect mean differences between treatments (P < 0.05). The results showed that year 2010 and 2011 belonged to two extreme climate types, i.e. phased extreme drought and whole extreme drought within the growth period. For both years, extreme drought climate led to "dried soil layer" phenomenon in the soil profile of 60-100cm in all treatment groups. However, the treatment of ridge and furrow with plastic mulching (RFM) was observed to have a significantly positive effect on mitigating the occurrence of "dried soil layer". The RFM treatment resulted in a significant overall upturn in water storage amount in soil bulk at the harvesting period, with the increases in soil water storage by 41.2 mm in 2010 and 22.4 mm in 2011 in comparison with that of control group, respectively. In addition, water use efficiency and water productivity of RFM treatment were increased by 1.7 kg · hm^-2 · mm^-1 and 0.4 kg · hm^-2 · mm^-1 in 2010 and 6.5 kg · hm^-2 · mm^-1 and 9.8 kg · hm^-2 · mm^-1 in 2011 in comparison with those of control group respectively. The performance of RFM treatment was significantly superior to that of other treatments. It showed that RFM technology significantly enhanced the transformation efficiency from natural rainwater to soil water and crop water. On the other hand, above-ground biomass in RFM group was declined by 30.5% in 2010 and 67.42% in 2011 compared to that of control group, but the harvest index of RFM group was increased by 33.4% in 2010 and 55.6% in 2011 in comparison with that of control group, respectively. Furthermore, RFM treatment played a positive role in optimizing architecture traits of spike, increasing seed weight, kernels per spike and grain weight per spike. Our study indicated that the RFM system can optimize water resources distribution, mitigate temporal and spatial contradiction between water supply and water demand for oat crop production, and transform more photosynthates from vegetative growth to reproductive growth. In conclusion, the RFM system displayed great potential to relieve the occurrence of dry soil layer and improve water field productivity in rainfed oat field in 2010 and 2011. It can be argued that the RFM system could serve as an important ecological strategy in response to extreme climate events and improve food security in arid region.