As an abundant biomass of surface water, water hyacinth was used as an input material to produce bioethanol in this study. Steam explosion and alkaline pre-treatment were applied on the material before simultaneous saccharification and fermentation (SSF) process was carried out. Experimental data suggested the optimal enzyme dosage be 1.0 wt% of the dry mass of the biomass, and the mass of the material be up to 8.0 wt% of the whole mixture in a one-step loading procedure to obtain the climax efficiency after 78 h. The process does not need additional nitrogen nutrition, such as corn steep liquor (CSL), as those in other common lignocellulosic bioethanol processes, because water hyacinth itself contains much protein in its chemical composition. Protein content analysis showed that it was 17.2 wt% (on dry basis), similar to what reported in some published studies. The SSF efficiency was positively 72.8 % at the optimal conditions resulted out from the experiments. Such a convenient conversion of water hyacinth to bioethanol is not only meaningful in term of biofuel production but also in term of environmental treatment.