Vibrio fischeri is a bacterium that produces light, mainly in sea water. The glowing light from luminous bacteria is a specific function consisting of luciferase and luciferin. This ability of V. fischeri is a valuable application for researchers. In this study, the growth conditions were optimized for emitting light. We selected some factors can affect on bacterial growth such as temperature, pH and culture medium. 5 ml of sea water broth and 5 μl of V. fischeri were incubated in 15, 18, 21, 24 °C. Following that three concentrations of NaCl (1 %, 2 %, 3 %), Asp and Cys (0.005, 0.004 g) were used. The result showed that the best light emitting of marine bacteria was at 24 °C. Top relative light unit (RLU) for this optimization was 22 million. The result showed that we could use these optimized V. fischeri for checkup of water and food toxicity.