Introduction: Primary teeth have a higher pulp horn morphology and thinner enamel causes caries teeth have eas-ier bacterial invasion, rapid extending into pulp necrosis which need root canal treatment. Some natural materials which can developed as alternative of root canal irrigation materials were green betel leaf 0.5% and red betel leaf 6.5%. This study was done to determine the effectiveness of 0.5% green betel leaf (Piper betle L.) extract and red betel leaf extract (Piper crocatum) 6.5% in inhibiting the growth of mixed bacteria of non vital root canal’s decidu-ous teeth in vitro study. Methods: this research was post test only control group design using in vitro solid dilution method. Samples of mixed bacterial taken from 12 root canal of necrosis anterior deciduous teeth. These samples then tested with 0.5% green betel leaf extract, 6.5% red betel leaf extract and negative control only MHA media. The growth of the mixed bacteria counted using scoring method. Data were analyzed. Results: Mann Whitney test results showed that there were significant differences between the average effect of 6.5% red betel leaf extract and 0.5% green betel leaf extract. Conclusion: 6.5% red betel leaf extract was more effective than 0.5% green betel leaf extract in inhibiting the growth of mix bacterial root canals of non vital deciduous teeth in vitro. Further research needed to prove the effectiveness of these betel leaves as root canal irrigation materials in vivo study.