Objective To study the in-vitro antibacterial activity of Niaoluqing Decoction on Ureaplasma Urealyticum (Uu) . Methods Sixty-three clinical strains of Uu were identified to determine their serology and antibiotic susceptibilities by the metabolic inhibition test(MIT). These strains were subcultured for 3 generations and then cultured with Niaoluqing Decoction with a series of concentrations from 250 mg/mL to 0.48 mg/mL. The minimal inhibitory concentration (MIC) was determined when the color of culture medium did not change from yellow to red in 72 h.Results For 63 clinical strains of Uu, the range of MIC of Niaoluqing Decoction was from 0.48 mg/mL to 15.63 mg/mL,MIC50≤1.95 mg/mL,MIC90≤3.91 mg/mL. Clinical strains of Uu had a higher sensitive to Niaoluqing Decoction than to tetracycline(?2=18.38,P 0.05).Clinical strains of Uu including all of its serotypes had a higher antibiotic susceptibility to Niaoluqing Decoction (MIC≤3.91 mg/mL) except for serotype 11, 1, 2 in this experiment contains (MIC≥7.81 mg/mL). Conclusion Niaoluqing Decoction showed a significant in-vitro antibacterial activity on clinical Uu strains with different serotypes.