[Objective] The study aimed to make clear the optimum conditions for liquid and solid fermentation of natto.[Method] BN-4 strains of Bacillus natto was used as the tested material to research on the effects of some factors such as soybean broken degree,fermentation time and inoculation quantity in the solid fermentation of Natto on the growth and FPase of B.natto,discuss the cell concn.,protein concn.and FPase change in the liquid fermentation and confirm the optimum conditions for liquid and solid fermenta...