Abstract: Arthrobacter YB6 strain is an antagonistic bacterium against Ralstonia solanacearum. In the stability test, the ferment filtrat was sensitive to heat, acid-alkali and protease K, it had no antibacterial activity when the temperature was above 60℃, the antibacterial activity would decrease significantly under the condition of strong acid-alkali or the concentration of protease K over 1.5 mg/mL. However,the ferment filtrat had strong stability against light and UV. The antibacterial activity was still stable under the condition of UV irradiation for 5 h or 35 000 L light. The ferment filtrat had wide antibacterial spectrum, and had inhibiting effect against 8 pathogen in the test. It had the best inhibiting effect against Ustilago scitaminea Syd. and Fusarium graminearum, the bacteriostatic rate achieved 88.6% and 80.2%,respectively. The inhibition activity against R. solanacearum by the dipping inoculum method was the best in pot experiments and its biocontrol rate reached 65.0%.