The invention discloses a drip irrigation method for protected cultivation of tobacco based on reference crop water demand, which comprises the steps: (1) calculating daily reference crop water demand(evapotranspiration ET0) according to a formula based on meteorological data of a region in recent 10 years; (2) calculating daily drip irrigation quota according to the formula: Q=r*ET0*p; and (3) carrying out irrigation, to be specific, irrigating once every 6-8 days in root extending stage, single irrigation quota being a sum of daily drip irrigation quotas within 6-8 days; irrigating once every 2-4 days in prosperous growth stage, single irrigation quota being a sum of daily drip irrigation quotas within 2-4 days; and irrigating once every 4-6 days in maturation stage, single irrigation quota being a sum of daily drip irrigation quotas within 4-6 days. According to the invention, the irrigation amount is determined based on the water demand of each stage of protected cultivation of tobacco; compared with conventional full irrigation, the method has the advantages that the main agronomic characteristics of tobacco are not significant, the irrigation quota is decreased by 33.3%, theirrigation water utilization efficiency is increased by 66.0%, the utilization rates of nitrogen fertilizer and phosphorus fertilizer are respectively increased by 11.1% and 81.6%, and tobacco production benefit is can be improved.