The Lactococcus lactis K6 isolated from mussel is able to produce Nisin Z. In order to obtain the optimized conditions of Nisin Z production， a systematic optimization experiment in our study was conducted by using minimum inhibitory concentration （MIC50） as an evaluation index against Staphylococcus aureus. Initially， the effects of single factors including different culture media， initial pH of culture broth， inoculum amount， and incubation temperature and incubation period on Nisin Z were explored. Results showed that initial pH of culture broth， incubation temperature and incubation period had significant effects on the production of Nisin Z. Subsequently， response surface analysis based on the previously study on the three significant variables were used to optimize the conditions for Nisin Z production. The optimal conditions were obtained as follows： inoculum cultural amount was 0.5% （V/V）， initial pH of broth was 7.5， incubation temperature was 29.8 ℃ for 9 hours. Under these conditions， the MIC50 of Nisin Z reached 0.625 BU/mL that was 8-fold increasing against S. aureus compared to the original conditions. Importantly， Nisin Z showed complete killing （bacteriocide） mechanisms against S. aureus with 8 h. The predicted values were close to the actual values， indicating the established model in this study is applicable for the massive production of Nisin Z.