Abstract: In order to take full of advantage of leek seeds protein,this paper studied the effects of different fermentation conditions on the protease activity of Aspergillus niger in defatted leek seeds. According to the index of the protease activity in the fermented liquid,this experiment explored the effects of initial p H,inoculum size,substrate concentration and fermentation time on protease activity using single factor experiment and response surface methodology(RSM). The optimum process conditions were as follows:initial p H 2.95,inoculum size 10.0%,substrate concentration 7.00% and fermentation time 72.0h. Under this optional conditions,the protease activity reached 280U/m L.