In this study, four strains of Chlorella genus and four strains of Tetraselmis genus were investigated to research their in vitro hydrogenase activities and hydrogen productions. C.sp.-3 showed the second highest in vitro hydrogenase activity with 297.48 nmol H2/(μg Chla h) and the highest volume of H2 production with 10.246 μl/L among all the strains. Although T. sp.-3 exhibited a much low H2 production of 0.298 μl/L, its in vitro hydrogenase activity was the highest with 315.92 nmol H2/(μg Chla h). During the continuous culture of five weeks, the hydrogen production of C. sp.-3 reached the peak at 3rd weeks with 12.46 μl H2 per liter culture, and decreased subsequently. In contrast, that of T. sp.-3 increased slowly and gradually with the culturing time, and was much lower than that of C. sp.-3 at each culture phases. These results showed that hydrogen production was a complex process that was determined not only by strain types but also by other factors, and that both C.sp.-3 and T. sp.-3 in the 8 strains were the most promising ones in hydrogen production and were worthy of further research.