Potato is one of the main crops in the north foot of Yin Mountains in the Inner Mongolia. Optimizing the planting systems of potato can increase the yield of potato, prevent the degradation of soil fertility, and promote the sustainable development of agriculture. A long-term field plot experiment was conducted from 2009 to 2014 to study the effects of intercropping potato with vetch or with naked oat on the land productivities and water use efficiencies.The results showed that: the yield-increasing effects were strong and similar between the intercropping potato with vetch or with naked oat, Land equivalent ratios(LER) were 1.59-2.24 and 1.56-2.22, respectively. Water consumption increased or reduced insignificantly between different intercropping system, but there were significant differences in water consumption between different experimental years, the maximal reduction in water consumption were 25.1%, 23.7% and 25.5%, respectively. Intercropping system had obvious advantage in water use, they significantly improved the water use efficiency, (water equivalent ratios were 1.59-2.01 and 1.55-2.24, respectively), particularly for vetch and naked oat. In addition, the water use effect of intercropping system was closely related to the rainfall. In general, potato intercropping mode is beneficial to improve field productivity and water use efficiency, particularly for vetch and naked oat.