Abstract: The aim of this study is to ascertain the influence of temperature on the bio-hydrogen productivity of marine green algae Chaetomorpha sp. GAF99 in sea water bioreactor system by utilizing multiple regression analysis. The biohydrogen production by green alga cultures was measured periodically at different incubation temperatures of active biohydrogen production phase to generate a model as well as surface response. The generated model {P = 26.81015e (-0.1[(Te-22.6)2+(Tm-24.7)2])} relates production of H2 (mL) as a function of temperature at two daily measurements (i.e., Tm, Te). The results revealed that the model can give significant correlation ship between biohydrogen production and temperature of incubation according to ANOVA statistical analysis based on F and p tests. The model and surface response curve obtained in this study showed clearly that the optimum biohydrogen production was recorded at the dark period at 23.2°C.