The most effective chemical pretreatment method for Scenedesmus dimorphus was evaluated based on solubilization rate and saccharification yield. When 1% of S. dimorphus with 0.5 N of chemicals such as HCl, H_2SO_4, HNO_3, NaOH and KOH was autoclaved at 120℃ and 1.1 atm for 60 min, the solubilization rate was high with alkali chemicals while the saccharification yield was low compared to that with acid chemicals. The pretreatment efficiency was significant in order in HNO_3, HCl and H_2SO_4, however, HCl would be effective for field application considering the cost. The proper concentration and time to treat with HCl were concluded in 1 N and 10 min. In the conditions with 1 : 1 mixed acid chemicals such as H_2SO_4+HNO_3, HCl+HNO_3 and HCl+H_2SO_4, the solubilization rate was similar to that with single acid treatment, while the saccharification yield was enhanced about 34% in the mixed condition with H_2SO_4 and HNO_3 compared to that treated with H_2SO_4.