Bagasse was a waste of sugarcane milling process where it was very important to the fuel resource. In this study, the sugarcane bagasse was study to produced composites through the fabrication of sugarcane bagasse (SCB) as reinforcement in unsaturated polyester resin (UPR) with methyl ethyl ketone peroxide (MEKP) as the hardener. The composition ratios where 10 % of SCB and 90 % of UPR, ratio 20 % of SCB and 80 % of UPR and ratio 30 % of SCB and 70 % of UPR for treated and untreated SCB was used. Then, 4 g/L NaOH was used as the treatment for the fibre to determine the effect of the fibre treatment to the composites produced. The sample of treated and untreated biocomposites was investigate and test using the physical and mechanical testing through tensile test, flexural test, thickness swelling, water arbsorption and density. It was found that, the tensile stress was increase with decreasing of SCB used but the tensile strain and flexural strength was increase with increasing of SCB used. The thickness swelling and water absorption by the composites also increase with increasing of SCB used compared to high percentages of UPR used. The treatment of SCB was increase the density of the composites produced compare to used untreated SCB to produced the composites.