A novel process integration occupying high cell-density culture (HCDC) and simultaneous saccharification and fermentation (SSF) in one bioreactor achieved an efficient ethanol production in this study. The effect of inoculum sizes of S. cerevisiae for ethanol production in SSF was investigated. High ethanol production was obtained with high inoculums size of cells from 4 to 30 kg.m(-3). The process integration including HCDC and SSF in one reactor was achieved. A production of 35.2 kg.m(-3) cells was obtained with HCDC in aerobic conditions. Cellulase and pretreated corn stover were added into the fermentation broth in the same bioreactor, and the SSF procedure was initiated in anaerobic conditions. The highest ethanol titer of 17.08kg.m(-3) corresponding to 101.50% theoretical yield was obtained, and the peak value time was 24 h with beta-glucosidase addition in the HCDC-SSF system. The highest ethanol titer of 11.01 kg.m(-3), corresponding 65.41% theoretical yield, was obtained at 72 h with regular SSF.