Abstract: Effects of some ions and organic compounds on protease activities of Bacillus subtilis were investigated It was found that: ① Of 5 inorganic ions tested, Mg 2+ , Na + and K + were shown to activate the protease activities and Mg 2+ had the strongest effect on protease at 2 mmol/L The impacts of Na + and K + declined with decrease in concentrations, respectively. Zn 2+ and Ca 2+ inhibited the protease activities. ② All seven heavy metal ions were shown to have inhibition except Mn 2+ which activated the protease at three tested concentrations ③ Both cysteine and EDTA had the activated effects on protease activities and the effects were most remarkable at 20 mmol/L. ④The combinations of Na + and K + , Ca 2+ and Mg 2+ , EDTA and Cu 2+ all inhibited the protease activities to some extents