Abstract: Heavy Metal toxicities are assessed with Photobacteriumphosphoreum and the dose-response curvefor ZnSO47H2O, K2Cr2O7, HgCl2, CdCl22.5H2O and Pb(NO3)2 can be described by Weibull model while for CuSO45H2O can be described by Logistic model in which the values of Log2EC50 were easily predicted. The P.phosphoreum was most sensitive to Hg, followed by Zn, Pb, Cd, Cu, andthe least sensitive to Cr. The EC50 of the P. phosphoreum fell within the scope of the species sensitivity distribution model predicted with other marine organisms. Compare to fish, daphnia, decapods and bivalves, P. phosphoreum is at a low level of sensitivity to Cu2+, but at higher levels of sensitivities to Cd2+, Pb2+, Hg2+, Zn2+ and Cr6+. Most of the marine species have the same order of the response to the six different heavy metals, indicating that toxicity testusing P. phosphoreum is very important for predicting heavy metal effects in marine ecosystem.