Abstract: In order to understand the mechanism of the effects of different tillage systems on photosynthesis characteristics of flag leaf and water use efficiency(WUE) in winter wheat, experiments were carried out on slope farmland in Luoyang, Henan Province during 2003～2004. There were five tillage systems including reduced tillage(RT), no tillage(NT), two crops tillage(TCT), subsoiling tillage(ST) and conventional tillage(CT). The results indicated that Chlorophyll pigment contents with conservation tillage such as no tillage and subsoiling tillage were significantly higher than that with conventional tillage. At the flowering stage, the values of qP, qN and ΦPSⅡ with no tillage and subsoiling tillage were significantly higher than that with conventional tillage, but the 1-qP/qN values were significanty lower. At the intermediate grain-filling stage, the net photosynthetic rates of wheat flag leaf with no tillage and subsoiling tillage were 96.4% and 99.7% of those with conventional tillage, but the difference was not significant. Compared with conventional tillage, the grain yields with no tillage and subsoiling tillage were increased by 19.3% and 9.4%, and the water use efficiencies were increased by 17.5% and 8.5%.