This study aims to determine the physical characteristics of rice straw and highlights the presence of sugar in rice straw. The use of natural fibers as a reinforcement in construction has existed for millennia. They are mixed with clay to make building materials. This addition avoids cracks and sometimes contributes to flexural strength. Researchers have detected a high level of sugar in natural fibers. This sugar contained in the biomass is at the origin of the setting delay and the hardening of the building materials. Another not least significant defect found in natural fiber is its high water absorption potential. This hydrophilic character is due to the intrinsic porosity of the straws. This article aims to determine the physical characteristics of rice straw and highlights the presence of sugar in rice straw. First, the density and water absorption rate of the rice straw were determined. Then chemical tests were carried out to determine the rate of mineral constituents (ash), lignin, hemicellulose and finally the rate of cellulose is deduced. Like most crop straws, rice straw contains a high level of sugar. It also has a very low density compared to other building materials. It is around 450 kg/m 3 . Rice straw also has a high water absorption rate. The absorption rate absorption rate (At) 5 min of immersion in water, its absorption rate reaches 234%.