Abstract: In order to eliminate the hazards of foam in the process of hydrogen production by photosynthetic bacteria (PSB), tributyl phosphate, stearyl alcohol, rapeseed oil and sodium dodecylbenzene sulfonate were used as defoamers in the experiments. The results showed the hydrogen yield increased with addition of rapeseed oil and stearyl alcohol by 5.4% and 3.95%, and rapeseed oil and stearyl alcohol had better capability to decrease the foam than the others. The growth of PSB was inhibited by tributyl phosphate which was covered the surface of culture medium. To reach max cell concentration, the growth time of PSB increased by 48 h and hydrogen yield decreased by 17.88% when sodium dodecylbenzene sulfonate was used as the defoamer. The rapeseed oil economy adding amount was 0.05% when it was covered the surface of culture medium in the process of hydrogen production by PSB.