Abstract: OBJECTIVE To analyze the irrational drug use in children, and explore the roles of HIS presets combined with drug rules in the rational use of drugs in children. METHODS Through the automatic prescription screening by YiYao rational drug use system, the main problems were drug usage and the route of administration. Drug usage and administration routes were preset in HIS system. According to the particularity of children's medication, special rules were designed in the rational drug use system. RESULTS The proportion of irrational drug usage and wrong routes of administrations were declined after HIS presetting, which was from 7.16% and 0.57% to 5.04% and 0.19%, separately. The proportion of errors in the dosage and route of administration was decreased from 3.44% and 0.29% in 2014 to 1.01% and 0.02% in 2016 respectively, and the ratio of the fourth and fifth alerts also dropped from 2.83% and 0.35% in 2014 to 1.07% and 0.11% in 2016 respectively. Thus, the qualified rate of prescriptions was effectively improved through the designing of children's special rules.CONCLUSION The presetting of HIS has obvious effect on prescribing rationality of physician, and the designing of children's specific rules can further improve the rational drug use. Integration of children's drug use resources and the development of artificial intelligent could help to improve the rational use of drugs in children.