This paper analyzed Mimusops elengi leaves, Averrhoa carambola leaves and Curcuma xanthorrhiza rhizomes extract. This study aimed to figure out flavonoid contain especially quercetin in the mixed herbs extract. Various particle size and amount of the mixed herbs were tested to determine effect of particle size and amount of substance to flavonoid content of the extract. The extract was analyzed using colorimetric method and thin layer chromatography (TLC). Thus, results of these analyses would depict high flavonoid content especially quercetin. Quercetin was present in the mixed herbs extract through TLC and colorimetric analysis. Through TLC method, flavonoid and quercetin content were measured. Optimum result was obtained by extracting mass of herbs 2.4 grams with particle size of 60 < D <16 mesh powder and dissolving them in 200mL of water. It was equivalent to 498.09ppm of quercetin concentration and total flavonoid content 41.51mg QE/g herbs. Further addition of mass of the mixed herbs caused decrease of flavonoid content due to equilibrium. Meanwhile, fine powder D ≤ 60 mesh had less interaction with solvent during extraction due to floating particles of mixed herbs. It led to less quercetin and total flavonoid content.