Abstract: Abstract: The crop productivity is low and unstable in arid and semi-arid region, and water is an important factor limiting crop yield. How to effectively use water and steadily increase crop productivity becomes the focus of attention. Broomcorn millet is one of important crops with large planting area in semi-arid region of Northern Shaanxi, China. In this study, the mechanism of increasing yield under film mulching on ridge-furrow for harvesting rainwater was investigated to provide theoretical support about high yield farming technology of broomcorn millet in arid and semi-arid areas. To explore the effects of film mulching on ridge-furrow for harvesting rainwater on photosynthesis characteristics and yield of broomcorn millet in semi-arid region of Northern Shaanxi, China, a three-year field experiment was conducted with four different widths of ridge and furrow from 2010 to 2012, and the bare land flat sowing as the control (CK). The width of ridge and furrow were 40 cm : 40 cm (P40), 60 cm : 60 cm (P60), 80 cm : 80 cm (P80), and 100 cm : 100 cm (P100), respectively. The field experiment used a randomized block arrangement with three replications. The plant density was 5.0×105 plants/hm2, and the average row spacing was 40 cm. Before sowing, soil preparation, fertilization and film covering had been performed. The organic fertilizer, urea and calcium phosphate were applied in 7 500, 75 and 75 kg/hm2, respectively. The white plastic film used in the experiment was 0.008 mm thick. Net photosynthetic rate, stomatal conductance and intercellular CO2 concentration were measured at 9:00-11:00 am on sunny and windless day, and yield traits were measured in the maturity stage of broomcorn millet. The results showed that film mulching on ridge-furrow for harvesting rainwater could significantly increase the photosynthetic rate and stomatal conductance, and decrease the intercellular CO2 concentration at each growth stage of broomcorn millet. With the increase of ridge and furrow width, the photosynthetic rate and stomatal conductance increased at first and then decreased, and the intercellular CO2 concentration decreased at first and then increased in the same growth stage of broomcorn millet. The film mulching on ridge-furrow for harvesting rainwater had little influence on main agronomic characters, but increased significantly plant height and yield of broomcorn millet. The photosynthesis of broomcorn millet was controlled by non-stomatal factor at each growth stage, and film mulching on ridge-furrow for harvesting rainwater could reduce the non-stamatal limitation on the photosynthesis significantly. In conclusion, film mulching on ridge-furrow for harvesting rainwater could enhance leaf photosynthesis capacity, improve broomcorn millet yield formation variables, and the treatment P60 was the best among all the treatments, which could be recommended as an efficient planting pattern in the production of broomcorn millet in semi-arid region of Northern Shaanxi, China.