The fermentation time of patented strain Mr-99 is about 24 hours. This strain is a monascus strain with high yield of extracellular polysaccharide by liquid fermentation. After the optimization of liquid fermentation medium and fermentation conditions, the highest extracellular polysaccharide yield can be reached within 24 hours, and the highest can reach18.6 g/L. This fermentation time is short, which is suitable for the efficient preparation of polysaccharides in the production process.