Introduction Mixed dentition age is a stage when there were both primary and permanent teeth in mouth, on children between 6-12 years old. There are 80-95% of children under 18 years old who have caries. Caries lesion may become worse if salivary flow is low. Saliva has important roles on tooth remineralization to prevent caries. Purpose The aim of this research was to determine the differences of salivary flow rate between children with low caries index and high caries index. Materials and Method This was an analytic observational research that used cross sectional design. Subjects are children between 6-8 years old in Padokan 2 elementary school which selected by purposive sampling technique. Salivary flow rate was measured from unstimulated saliva that collected in pot sample and divide it by total time (3 minutes) and the result is calculated in millimeters per minute. Result The results showed that the mean value of salivary flow rate in children with high caries index is 0.429 ± 0.126; and children with low caries index is 0.847 ± 0.349. Statistical analysis used Independent t-test showed that there was significant result (p<0,05). Conclusion In conclusion, there was significantly difference in salivary flow rate between children with low caries index and children with high caries index.Children with low caries index have higher salivary flow rates than children with high caries index. Key words: children 6-8 years old, high caries index, low caries indeks and salivary flow rate