A highly phytase-producing strain B.licheniformis LL8 was obtained by several mutagenesis of UV with B.licheniformis as starting strain.The new strain produced about two folds of phytase activity as compared with the starting strain. The production performance of the strain was stable. The cultivation conditions were optimized by single factor and orthogonal experiment. When the mutant B.licheniformis LL8 was cultivated at 55℃, initial pH 7.5 with the inoculation size of 10% for 30h in WBE medUm, the phytase activity was up to 2268.4U/mL.