This study aims to determine the best levels of bioethanol from a combination of cassava peel and pineapple peel mixture with a variation of yeast mass as much as 11 grams, 13 grams, 15 grams and 72 hours fermentation time, to determine the optimum yeast mass and determine ethanol levels according to SNI. This research was carried out by hydrolysis or boiling of cassava and pineapple peels using 30 minutes of distilled water to break down molecules into two parts, then fermentation process using Saccharomyces Cerevisae (yeast) and distillation process using a destilator to obtain ethanol from fermentation which is then tested with a Pen Refractometer to determine whether there is an ethanol level formed from the distillation process. The best sample selected was then tested for ethanol content using the Gas Chromatography tool. The results of this study are known by using the Gas Chromatography tool to find out the ethanol content contained in the distilled sample, the highest ethanol content of each combination mixture is for a combination of 100% cassava peel - 0% pineapple peel 87.4% in yeast mass 15 grams, a combination of 75% cassava peel - 25% pineapple peel 88.6% in a 15 gram yeast mass, a combination of 50% cassava peel - 50% pineapple peel 89.3% in a 15 gram yeast mass, a combination of 25% cassava peel - 75 % of pineapple peel is 87.3% in a yeast mass of 15 grams, and a combination of 0% cassava peel - 100% pineapple peel is 36.8% in a yeast mass of 15 grams. So it can be concluded that the ethanol content of the combination of cassava peel and pineapple peel is not included in the category of Indonesian national standards (SNI).