Introduction: The problem of dental caries still needs to be considered by looking at around 60-70% of elementary school children in Pagak, Malang Regency. The caries incidence is associated with the problem of consuming drink-ing water with a very high calcium content of 165 mg/L. The purpose of this study is to analyze calcium deciduous teeth due to PDAM Pagak water consumption and correlate it with the incidence of childhood dental caries in Pagak. Methods: This research uses screening results in the form of a SiC index and 20 deciduous teeth samples were then divided into 4 groups, namely the sample group with a concentration 8,125%, 16,25%, 32,5% and 65% HNO3. Results: The results of the statistical test with the Kruskal Wallis test obtained a significance value of 0,002 which means there are significant differences in calcium content between the four groups. Based on the Spearman correla-tion test obtained a significance value of 0,00 and a correlation coefficient of 0,853 which means that there is a very strong and unidirectional relationship between the calcium content of deciduous teeth and children’s dental caries. To see the effect, the r2 value of 0,853 means that the deciduous tooth calcium effect on the incidence of child dental caries in Pagak District is 85,3%.To see the enamel microporosity with a high Ca in the Desidui tooth obtained from SEM-EDX analysis of 41.96% of other elements contained in the tooth (oxygen, natrium, silicate, Magnesium,Posfor, kalium) and there are special characters of calcium, its spread on each side of a single-sided dental preparation, and can decay due to the acid resulting from bacteria in the mouth resulting in saliva becoming more acidic. So that the teeth become fragile (demineralization of Apatit hydroxylation) and affect the occurrence of remineralization of apatit hydroxy. Conclusion: The conclusion of this research is there is a relationship between calcium content of deciduous teeth due to the water consumption of PDAM Pagak and Wonokerto with the incidence of children’s dental caries in Pagak and Wonokerto.