Star fruit (Averrhoa bilimbi) contains active ingredients such as flavonoids, tanins, and saponins that can inhibit and kill bacteria, including bacteria that cause gingivitis. The purpose of this study is to test the inhibition extracts of star fruits (Averrhoa bilimbi) against the bacteria that cause gingivitis in patient with fixed orthodontic appliance in vitro. The design of this study was pure laboratory experimental use of swab-causing gingivitis bacteria in GCF users of fixed orthodontic appliances. The concentration used for belimbing wuluh extract was 12.5%, 25%, 50%, and 100% and aquades (negative control) and chlorhexidine 0.2% (positive control). Antibacterial power test using diffusion. Data analysis using One Way Annova test and LSD test. Positive control shows a radical zone of 7.65 mm, at 12.5% concentrations 3.21 mm, at 25% concentrationis 3.92 mm, at 50% concentration is 4.70 mm and at concentration of 100% extract that is equal to 6.51 mm. The result from this study is indicate that extracts of star fruits can significantly inhibit the growth of bacteria that cause gingivitis (p = 0.000, p <0.05). This study shows that all concentration of star fruit extract is effective to inhibit bacteria that cause gingivitis. 100% concentration is the most effective extract concentration for inhibiting bacterial populations that cause gingivitis.