Neutral protease strain ZH-6 was isolated from soil sample. Single factor experiments and orthogonal experiments were conducted, and the results showed that under the conditions as follows: fermentation time 48 h, fermentation temperature 33℃, rotation speed 180 rpm, initial pH 6.5 with the fermentation culture medium (corn-starch 2.0%, wheat-bran 3.0%, Na2HPO4·12H2O 0.4%, KH2PO4 0.03%, ZnCl2 0...