Objectives : The aim of this study was to investigate weight gain effects of the Sungjangjeungbo-tang (Ch$acute{e}$ngzh$check{a}$ngz$ar{e}$ngb$check{u}$-tang) on thin Korean preschool children. Methods : Sungjangjeungbo-tang is composed of 9 herbs for treating indigestion. We analyzed 119 preschool children who visited Kim Kijoon Oriental Clinic BOM from Jan. 1, 2006 to Aug. 31, 2011 with three criteria: 1) 2~5yrs of age and BMI < 50th percentile on the baseline visit; 2) the child had taken the Sungjangjeungbo-tang for 1~3 month(s); and 3) the clinic had records of both height and weight on the baseline and at least once over 1~3 month(s). Results : Sungjangjeungbo-tang significantly improved BMI percentile in all groups. The changes in BMI percentile variations were larger in the 3 months group than in other groups, but not significantly. Gender, age and BMI on the baseline had no significant effects on the effectiveness of Sungjangjeungbo-tang. Conclusions : Sungjangjeungbo-tang positively affected on weight gain in thin Korean preschool children within 1~3 month(s) of treatment. However, additional studies on functional dyspepsia or the change of energy intake were needed to know the factors related to weight gains.