The invention belongs to the field of microorganism technology, and discloses a cordyceps sinensis fluid medium. The cordyceps sinensis fluid medium is prepared from 50 to 60g of a fibrous material, 50 to 60g of a vinasse hydrolysate, 70 to 80g of potato extraction solution, 30 to 40g of glucose, 2g of magnesium sulfate, 1g of streptomycin, 1g of penicillin, and 0.01g of vitamin B1. A preparationmethod comprises following steps: the above ingredients are delivered into a container, an obtained mixture is diluted with water to 1L, the pH value is adjusted to 6.5 to 6.8, sterilization in an autoclave is carried out, wherein the pressure is maintained for 15min when the temperature is increased to 121 DEG C, an obtained product is taken out from the autoclave, and is cooled to room temperature. The invention also discloses a method used for culturing cordyceps sinensis with the cordyceps sinensis fluid medium. The cordyceps sinensis fluid medium is reasonable in composition, and low in cost; and the quality of cultured products is improved greatly.