The fermentation conditions and properties of the thermostable protease from a thermophilic strain BY25 were studied. BY25 was able to grow at temperature up to 55℃, yet the fastest growing rate was achieved at 50℃. And the best fermentation conditions for BY25 to produce protease was at 30℃, with initiating pH of 8.0, and with glucose as carbon source. High oxygen supply was crucial for protease production. Up to 4 170 U of protease in 1 ml of fermented culture medium could be achieved under such condition. The enzyme was identified as thermostable neutral metalloprotease, with highest activity at 55℃, pH 7.0, and exhibited high temperature tolerance and good stability at a wide range of pH. EDTA could inhibite enzyme activity greatly, Fe2+ and Cu2+ also had negative effects on enzyme activity.