The invention relates to a method for producing a cordyceps sinensis feed additive and a product, and belongs to the technical field of feed fermentation. The method comprises the following steps: firstly, quickly producing a large amount of mycelia through liquid fermentation by taking low-price beer dry yeasts and beer grains as raw materials; secondly, inoculating a large amount of mycelia into a solid culture medium for solid fermentation. According to the method, shallow tray type static and solid fermentation equipment is adopted for fermentation and is simple and convenient to operate, the fermentation cycle is short, the pollution is alleviated, the production cost is reduced, and the cordyceps sinensis mycelia can be efficiently produced to serve as the feed additive.