This study investigated the effect of the three spoilage bacteria (Carnobacterium maltaromaticum, Shewanella putrefaciens and Aeromonas salmonicida) on the development of melanosis by inoculating the bacteria on modified atmosphere packaged shrimp. The three bacteria, which inoculated at about 5logcfu/g, proliferated to a maximum level of 7.49, 6.86 and 6.89logcfu/g, respectively at the end of storage. In regards to the effect of bacteria on melanosis, it was found that C. maltaromaticum did not display a significant effect on PPO activity and melanosis, and A. salmonicida showed an inhibitory effect on PPO activity with an activity value of less than 1.5Units/ml. However, the PPO activity of shrimp inoculated S. putrefaciens was about one time higher than other samples and greater melanosis was displayed in the first 48h. As melanosis can cause sensory quality loss, the growth of S. putrefaciens should be limited.