Abstract: The detection of water toxicity by bioluminescent bacterium was restricted because the stability of commercially available lyophilized powder varied among different batches and long resuscitation time.The cultivation of Photobacterium phosporeum was scaled up from shake flask to 5 L fermenter in order to obtain bacteria with stable luminosity.The optimum culture conditions in shake flask were as follows:18 ℃,pH 7.0,rotation speed 200 r/min and inoculation amount 2%,under which the specific luminosity can reach 2 500 mV.In 5 L fermenter,the optimum conditions were as follows:rotation speed 200 r/min,aeration rate 0.5 vvm and dilution rate 0.10 h^-1,under which the specific luminosity during the continuous cultivation ranged from 500 mV to 1 000 mV in several batches,and the continuous cultivation was maintained for about 10 d.