Background : Platycodon grandiflorum root(PGR) was one of the primary herbs used in a phlegm-relieving herb from the past. Purified platycoside compounds from the roots of PGR may exhibit neuroprotective, antimicrobial, anti-inflammatory, anti-cancer, anti-allergy, improved insulin resistance, and cholesterol-lowering properties. To evaluate preference and functionality of PGR extracts, PGR was fermented by several lactic acid bacteria. Lactic acid bacteria used were Leuc. mesenteroides N12-4 and N58-5, L. plantarum N76-10 and 56-12, L. brevis N70-9 and E3-8. Methods and Results : This study was performed in order to investigate the changes of platycosides, as well as the antimicrobial activities on bronchus diseases inducing bacteria(C. diphtheriae, K. pnneumoniae, S. aureus, S. pyogenes) of Platycodon grandiflorum root(PGR) fermented by using lactic acid bacteria(Leuc. mesenteroides N12-4, Leuc. mesenteroides N58-5, L. plantarum N76-10, L. plantarum N56-12, L. brevis N70-9, L. brevis E3-8). Growth of L. plantarum on PGR was the most active during lactic acid fermentation by some different strains. Total platycoside, platycoside E, platycodin A, polygalacin D2, polygalacin D and diapioplatycoside E contents of PGR fermented for 96 hours at 37℃ by Leuc. mesenteroides and L. plantarum were increased, while platycodin D and platycodin D3 were decreased. The antimicribial activity on PGR fermented by L. plantarum N56-12 exhibited a strong microbial proliferation in all four kinds of bronchus diseases inducing bacteria and was higher than non-fermented PGR extract. Conclusion : Thus, this results showed antimicrobial activities on bronchus diseases inducing bacteria and platycosides content of PGR by L. plantarum N56-12 were higher than non-fermented PGR extract.