Cassava constitutes an abundant substrate in tropical regions. The production of butanol in bio-butanol fermentation by Cl. acetobutylicum using cassava pulp and the concentration of Cl. acetobutylicum was scaled-up. The purpose of the project of verifying the effect of initial cell concentration of Cl. acetobutylicum on bio-butanol fermentation from cassava pulp. Found that the bacteria Cl. acetobutylicum concentration 106 has the ability to produce organic solvent as much as possible. It was found that the yield (Yield) will increase from 0.19% to 0.31% when the concentrations of bacteria Cl. acetobutylicum of 104 CFU / ml constitute 105 CFU / ml and will increase from 0.31 % to 0.35 % when increase the concentrations of bacteria Cl. acetobutylicum of from 105 CFU/ml constitute 106 CFU/ml. Then, it's decreased from 0.35% to 0.32% when the concentration of bacteria Cl. acetobutylicum of 106 CFU / ml constitute 107 CFU / ml. From the data using the concentration of bacteria Cl. acetobutylicum in the production of organic solvents at high concentration. Will affect the amount of butanol polls. So, when we increased the concentration of bacteria Cl. acetobutylicum. Too high will result in a decrease in the yield. Results suggest that the use of cassava as a substrate in bio-butanol fermentation could be a cost-effective way of producing butanol in tropical regions.