Carotenoid compounds are popular natural antioxidants which are commonly isolated from the plants. Recently, there have been many researches on carotenoid biosynthesis towards low cost products. In this study, Rhodotorula sp. was grown on an agricultural byproduct (corncobs) as a matrix in solid-state fermentation. Essential nutrients were added with different concentrations to optimize condition for the carotenoid biosynthesis. Effects of other environmental factors such as moisture content and fermentation time on the yield were also characterized. The optimal nutrient composition for the yeast’s growth and carotenoid biosynthesis is a compound of 500μg nitrogen and 16mg carbon in 100g matrix. Additionally, the moisture content of 80% is the best for producing carotenoid by this yeast strain. The fermentation time for the highest carotenoid yield is observed after 8 days