Objective To improve the utilization of waste Xinhui mandarin pulp and explore the feasibility of preparing low-cost carotenoid-producing culture media.Methods By using Xinhui mandarin juice as the fermentation medium, with the total carotenoid yield and biomass of rhodotorula mucilaginosa as the evaluation indexes, the components of the medium and fermentation conditions were optimized via single-factor experiments and response surface methodology.Results The fermentation medium is prepared with Xinhui mandarin juice, with the total sugar content controlled at 95~100 g/L, total nitrogen content at 3 g/L, and initial pH at 6. Under the conditions of 4 mL/100 mL inoculum size, 240 r/min shaker rotation speed, 0.08 liquid loading coefficient, 28 ℃ fermentation temperature, and 96 h shake-flask fermentation, the biomass of rhodotorula mucilaginosa reaches 44.62 g/L, and its carotenoid yield reaches 13.08 mg/L. The DPPH radical scavenging activity of the pigment extract obtained under these conditions is higher than that of Vitamin C.Conclusion Compared with the basal medium under the same fermentation conditions, the shake-flask yield of carotenoid from the Xinhui mandarin juice medium increases by 2.17 times, which provides a new approach for the efficient exploitation and utilization of waste Xinhui mandarin pulp.