Background: Bad breath is a problem caused by bacteria, one of the main causes of oral problems is in the root canal, root canal treatment failure is caused by the bacterium Enterococcus faecalis. Mouthwash preparations with an active ingredient of pineapple peel ethanol extract as antibacterial have the advantage of being able to clean the cavity that is difficult to clean. This study aims to identify flavonoid compounds that have antibacterial activity. Method: Making pineapple peel extract (Ananas comosus, L. MERR) using maceration method using 70% ethanol as solvent. Determination of Ethanol Levels Using the GCMS Method. Mouthwash preparation evaluation includes Organoleptic, pH measurement, Specific gravity, Viscosity, and Cycling test. Result: One Way ANOVA results from the cycling test showed good quality mouthwash preparations. Conclucion: In the antibacterial test on F3 the ethanolic extract of pineapple peel had the highest antibacterial activity against Enterococcus faecalis with an inhibition zone diameter of 19.15 mm. Determination of quercetin levels by KLT-Densitometry method showed the presence of quercetin compounds in extracts and mouthwash preparations.