Broad bean (Vicia faba cv. Lincan II) were grown in pots at two CO 2 concentrations (350 and 700 parts per million by volume (ppmv)) and three soil water levels (80, 60 and 40% field water capacity) in field open-top chambers (OTC f ). Water deficit reduced plant shoot dry weight, bean yield, and water use efficiency (WUE) by over 40, 30, and 15%, respectively, with higher relative reduction under elevated CO 2 . High CO 2 significantly increased leaf photosynthesis, plant growth, bean yield and WUE. The increase is significant only at sufficient water supply. Both CO 2 enrichment and water deficit influenced bean yield mainly through bean number. Harvest index was increased by both high CO 2 and drought. There were significant interactions between CO 2 enrichment and soil water deficit on plant growth and yield. On the basis of above results, it is concluded that the effects of CO 2 enrichment on plants depend on soil water status, and the negative effects induced by drought will be relatively more serious in the future at increased CO 2 concentrations.