To study the effect of culture medium on hydrogen production by the marine green algae, Platymonas subcordiformis under sulfur deprivation, cell growth, hydrogen production, and starch and protein catabolism was investigated in the work. Algae cells cultured only in optimized medium required 6~8 days to reach the late logarithmic at the approximate density of $(2.00pm0.18) imes10^6$ cells/mL, which in traditional medium needed 18~22 days to reach $(1.85pm0.20) imes10^6$ cells/mL. Increased levels of Chlorophyll ($10.74pm0.20;{mu}g/mL$), starch ($149.50pm6.15;{mu}g/mL$), and protein ($213.00pm7.36;{mu}g/mL$) were accumulated in optimized medium, which were 1.06, 1.47, and 1.87-fold of the algae cells cultured in traditional medium, respectively. The sealed culture of algae cells in sulfur-deprived optimized medium shifted to anaerobic conditions after 96 h of light illumination and produced $0.45pm0.12;mL$ $H_2$, but in traditional medium maintained aerobic condition and no hydrogen was produced. In addition, changes in starch and protein content during continuous light illumination indicated that more endogenous substrate was consumed in the sulfur-deprived optimized medium than that in the sulfur-deprived traditional medium.