Abstract: Objective To examine age-specific mortality rate and the main cause-specific mortality rate among children under 5 years old in Guizhou province from 1991 to 2015 for evaluating the improvement in indicators of “the Fourth Millennium Development Goal (1991-2015)”.Methods Neonatal mortality rate (NMR),infant mortality rate (IMR),under 5 years old children mortality rate (U5MR),and the main cause of death of under 5 years old children in rural and urban areas of Guizhou province from 1991 to 2015 were analyzed statistically using data extracted from Mortality Surveillance Network for Children under 5 Years Old.Results The NMR,IMR and U5MR were 3.5‰,8.7‰,and 12.2‰ in Guizhou province in 2015 and the rates were reduced by 92.9%,86.8%,and 87.6%,respectively,compared to those in the year of 1991.The mortality rate among the children were declined yearly both in rural and urban areas.From 1991 to 2015 in both rural and urban areas,the NMR was decreased from 25.0‰ to 3.2‰ and from 55.3‰ to 3.6‰; the IMR was decreased from 39.9‰ to 7.6‰ and 93.0‰ to 9.2‰; and the U5MR was decreased from 42.1‰ and 112.4‰ to 10.3‰ and 13.2‰,with significant differences (P<0.01 for all).The NMR,IMR,and U5MR in the rural areas were 1.28,2.63,and 1.13 times higher than in the urban areas in 2015,while those rates were 2.67,2.33,and 2.21 times higher than those in 1991.During the 25 years in Guizhou province,significant decreases in specific mortality rate for the main causes of death among the children under 5 years old were observed,with the decreases of pneumonia (from 3 276.1 to 215.3 per 100 000),diarrhea (1501.7 to 61.6),asphyxia (1416.7 to 154.4),premature or low birth weight (689.4 to 153.7),and meningitis (689.4 to 4.7),respectively (P<0.01 for all).In 2015,the top four major causes of death were pneumonia,asphyxia,premature or low birth weight and congenital heart disease for all the children death under 5 years old in Guizhou province,while for the children in urban areas the four causes were pneumonia,premature or low birth weight,congenital heart disease,and asphyxia and for those in rural areas the four causes were pneumonia,premature or low birth weight,asphyxia,and congenital heart disease,respectively.The mortality rate of pneumonia,asphyxia,and premature or low birth weight were declined year by year,but the mortality rate of congenital heart disease,drowning,and road traffic accidents fluctuated.Conclusion The U5MR was 12.2‰ in Guizhou province in 2015,reaching the national target of 2020; but U5MR in rural areas and urban-rural gap in the rate need to be reduced and focal points in disease control and prevention should be adjusted according to variations of proportional mortality rate in the province.