Abstract: To investigate the effects of new composite water retention agents on the production of flue-cured tobacco in semi-arid areas, we investigated the effects of classical water retention agents (polyacrylate water retention agent and polyvinyl alcohol-acrylic acid water retention agent) and new composite water retention agents (biochar composite water retention agent and potassium humate composite water retention agent) on growth, activities of key enzyme in carbon, nitrogen metabolism, organic acids and conventional chemical composition of flue-cured tobacco through field trials, with no water retention agent as control. The results showed that biochar composite water retention agent and potassium humate composite water retention agent were more effective than the classical water retention agents in increasing the maximum leaf length and root volume, promoting carbon and nitrogen metabolism of tobacco leaves, and increasing the activities of amylase (AL), neutral transforming enzyme (NI) and nitrate reductase (NR) in tobacco leaves. The biochar composite water retention agent and potassium humate composite water retention agent could significantly increase the total non-volatile organic acids in tobacco leaves. The potassium humate compound water retention agent was more effective, increasing malic acid and citric acid contents by 16.8%, 29.8% and 30.5%, 27.9%, respectively, compared with the control. The treatments also increased the contents of total sugar, reducing sugar, nicotine, potassium and chloride and sugar to alkali ratio in tobacco leaves. Application of new composite water retention agents can be beneficial in promoting flue-cured tobacco production in semi-arid areas.