Abstract: Intercropping is an efficient way to increase natural resource use efficiency and reduce the obstacles resulting from continuous cropping. However, little research has focused on yield increment mechanisms associated with potato and legume intercropping utilizing furrow-ridge planting with plastic mulch. A 4 years (2011-2014) field study was conducted at the Dingxi Experimental Station, Gansu Academy of Agricultural Sciences (104°36' E, 35°35' N), located on the northwest Loess Plateau. Potato (xindaping) and fababean (lincan131)were used during the study. Three treatments were imposed: 1) potato monoculture, 2) fababean monoculture, and 3) intercropped potato-fababean. Measurements included seasonal and yearly soil water content, crop productivity, crop seasonal water consumption, water use efficiency, individual species competitiveness and subsequently, land equivalent rate calculated. The paragenesis period of potato and fababean was more than 100 days; evaportranspiration in this period accounted for 42.5%-58.3% of total evaportranspiration of the intercrop treatment, and 68.2%-86.3% of total evaportranspiration for the potato treatment. The intercrop produced lower yields, 18.1 % and 31.2% in 2011 and 2014 respectively compared with the potato treatment. Crop water use efficiency was also lower in the intercrop. However, the intercrop yield was significantly higher (10.6%) in 2012 compared with the potato treatment. The land equivalent rate reached 1.3-1.5 and the competitiveness of fababean relative to that of potato ranged from 0.31-1.15 through the 4 years of the study. Intercropping could increase potential productivity under plastic mulching and ridge-furrow planting systems in semiarid areas, but selecting appropriate crop species for intercrop systems is necessary to increase both crop productivity and natural resource use efficiency, as well as improve the cropland environment.