Abstract: Background and Objective: Heavy metals showed an important environmental problem today. They can be toxic when they are present in excess. Their dangerousness is not only their ubiquitous presence, but also the fact that they exist in several chemical forms. Among the main metal extraction is mercury, its extraction has modified the proportion and the chemical form of this metal in various compartments of ecosystems making it bioavailable and potentially harmful for organisms especially human being. This study evaluated the toxicity of this metal and a bioluminescence method has been optimized. Methodology: Bioluminescence method consisted to optimize the intensity and stability of luminescence emitted by bacteria Vibrio fischeri (V. fischeri) strain NRRL-B-11177 cultivated in a modified LBS medium. Through this method, toxic effects of inorganic mercury (HgCl2) on V. fischeri have been determined. All data were analyzed using GraphPad Prism and values were obtained as means±standard errors. Results: Results showed aeration (600 mL min–1) and agitation (250 rpm) were essential to V. fischeri to emit light. It has found that at concentration 1.4 mg L–1, HgCl2 was capable to inhibit totally the light emitted by V. fischeri. Conclusion: Thereafter, evaluated the detoxification of HgCl2 in fluidized bed reactor using immobilized and free bacteria Escherichia coli strain R100 by the luminescence of V. fischeri.