Objectives : The purpose of this study was to correlation between the index of dental caries in primary teeth and the habits of diet and snack which are expected to influence on the index. The subjects of this study were 165 parents of the children who visited a pediatric dental hospital located in Gyeong-gi do from Jun. 15th to Sep. 26th, 2009, and the self-report questionnaire survey was performed. Methods : A questionnaire used in a previous study was revised and completed for this study and it consisted of 15 items on general characteristic, nine items on dietary habit, and five items on snack intake habit. The collected data was analyzed using SPSS program and findings are as follows Results : 1. The index of dental caries in primary teeth by ages was that children of four years old has 4~5 with 27.5%, children of five years old has 2~3 and 4~5 with 33.3% and children of six years old has 1 and 8~9 with 25.6%, showing a statistically significant(${chi}^2$=37.72, p<.01). 2. The frequency of brushing teeth was found to have statistically significant negative correlation with the number of primary teeth with dental caries (${chi}^2$=61.20, p<.001). 3. The frequency of taking snack was found to have statistically significant positive correlation with the number of primary teeth with dental caries (${chi}^2$=51.42, p<.001). 4. The desirability of dietary habit was found to have statistically significant negative correlation with the number of primary teeth with dental caries (${chi}^2$=36.51, p<.001). 5. The frequency of taking biscuit was found to have statistically significant positive correlation with the number of primary teeth with dental caries (${chi}^2$=67.74, p<.001). 6. The frequency of taking bread was found to have statistically significant positive correlation with the number of primary teeth with dental caries (${chi}^2$=29.63, p<.01). 7. The frequency of taking caramel and candy was found to have statistically significant positive correlation with the number of primary teeth with dental caries (${chi}^2$=38.85, p<.001). 8. The frequency of taking soft drinks was found to have statistically significant positive correlation with the number of primary teeth with dental caries (${chi}^2$=52.92, p<.001). 9. The frequency of taking ice-creams was found to have statistically significant positive correlation with the number of primary teeth with dental caries (${chi}^2$=75.07, p<.001). Conclusions : Those findings show that the children with undesirable dietary habit and higher frequency of taking snack have higher index of dental caries in primary teeth, therefore, it is considered that the regular brushing teeth and establishment of desirable dietary habit are very important for keeping health oral cavity. It is recommended that the continuous concern and repeated learning are needed in house and group of rearing infants so that the children take foods of fruits which have function of self-purification than the food of carbohydrates which has high adhesion and level of sweetness.