Rice straw is one of the very abundant lignocellulosic waste and does not interfere with the availability of food. Lignocellulose can be broken down into simple sugars and fermented into bioethanol with the help of yeast. Lignin which is very strong in lignocellulosic materials resulting lignocellulose breakdown cannot occur directly and require pretreatment to destroy the lignin. Mechanical pretreatment is one of the methods that can be developed in the hydrolysis of lignocellulosic compounds using Liquid Hot Water methods. The research was conducted by comparing the 3 variations of mechanical pretreatment (regular heating, heating with additional heating with pressure and high pressure) and 3 variations of the operating time (1 hour, 2 hours and 3 hours). Hydrolyzate obtained, fermented using yeast Saccharomyces cereviceae with concentration of 3%, 5% and 10% for 72 hours. The purpose of this study was to obtain a variety of methods, mechanical pretreatment time and the best yeast concentration in breaking the bonds of lignocellulose. The results showed that the best mechanical pretreatment is heating under high pressure within 2 hours of operating with ethanol content of 9.35% and 1.47 g biomass. The concentration of yeast to get the highest biomass and ethanol was 5%.