Objective: To observe the activity of Platycodon grandiflorum saponin (PGS) against Ureaplasma Urealyticum(Uu) through experiments of MIC, MBC , TIME-KILL and rapid bactericidal action. Method: MICs and MBCs were determined by broth microdilution method. The concentration of Uu was detected by quantitative PCR after diferent incubate time. Result: MICs were 16-32μg•mL-1 while MBCs were 32-64μg•mL-1 for PGS against Uu in vitro. Replication of Uu in PPLO was inhibited  by PGS when the concentration was between 16 and 32μg•mL-1. The number of Uu in PPLO broth was reduced and the growth was completely inhibited when the concentration of PGS reached 64μg•mL-1. The growth of Uu was inhibited after mixed with PGS for 1min in the concentration of 64μg•mL-1. Conclusion: PGS has anti-Ureaplasma Urealyticum activity in vitro, and could inhibite the growth of Uu rapidly.