Abstract: Water resources shortage is a key factor restricting agricultural production and sustainable socio-economic development in the northwest inland arid regions of China. Also technical production efficiency, agricultural water waste and inefficient water use in inland arid farming regions contribute immensely to water resources shortage. To this end, an empirical research was conducted using a combination of experimental investigation and quantitative analysis in the middle reaches of Heihe River, the northwest inland arid region of China. The results showed that farmer technical production efficiency (TPE) in the region was significantly higher than irrigation water use efficiency (WUE). The farmer average TPEs for Minle County and Linze County were 83.82% and 83.16% with mean irrigation WUEs of only 24.54% and 22.16%, respectively. Assuming no efficiency loss, it implied that the unit outputs of wheat in Minle County and seed corn in Linze County successively increased by 16.18% and 16.84% under present technical production conditions. This also suggested that compared with the minimum feasible water input under the present input-output conditions, about 75.46% of the water resources was wasted in wheat production in Minle County. Similarly, about 77.84% of water was wasted in seed corn production in Linze County. The result further indicated that farmer production inefficiency was mainly driven by TPE. While wheat TPE in Minle County accounted for 73.45%, other factors not controllable by farmers accounted for 26.55% of the production efficiency. Also for seed corn, farmer TPE accounted for 23.42% and other factors beyond farmer control accounted for 76.58% of the production efficiency in Linze County. Moreover, farmer TPE and irrigation WUE were obviously different for different farm/farming family sizes. The plot of management scale versus farmer TPE tracked an inverted U-shaped curve, with a stretched out co-rotation tendency of farmer irrigation WUE and management scale. The study also advanced and discussed several measures concerning enhancement of farmer irrigating WUE and TPE.