Objectives: To compare the mortality rate of children under ages five from different countries by their causes and to explore the cause of death that is relatively higher in South Korea and came up with measures for resolution. Methods: The statistics were based from section ICD(International Classification of Diseases)-10 of WHO(World Health Organization) Mortality Database. Among the OECD(Organization for Economic Cooperation and Development) countries, 15 countries with higher GDP(Gross Domestic Product) than South Korea were studied by the mortality rate from 2005 to 2010 sorted into two groups: 0 year group and 1-4 years group. Then the cause of death investigated in detail. Results: Among the 15 countries, average mortality of 0 year group in Korea ranked 8th and the average mortality of 1-4 years group ranked 4th out of 15. There were no significance in the mortality of 0 year group caused by any specific disease, but unnatural death was ranked 2nd after the United States. The natural death of 1-4 years group was ranked 6th, and the unnatural death was ranked 2nd after the Unites States. Among the natural deaths of 1-4 years group, the cause of death significantly higher was found to be disease G(nervous system disease). Among the subgroups of disease G, the orders went epilepsy, cerebral palsy, paralysis, and inflammatory disease. Conclusions: We have identified major causes of death of children under age 5. The highest proportion of cause of death in 1-4 years group was nervous system disease and we have proposed resolution. Henceforth, this data will be used as a foundational data for formulating policies relation to the Mother-Child Health.