Abstract: The change of the main nutriments of the medium and the metabolites during shake flash fermentation of Cordyceps militaris was investigated. The pH, total sugar, deoxidized sugar, free amino nitrogen and soluble protein was detected, and the growth of Cordyceps militaris and the production of crude polysaccharide and cordycepin were also determined. Results indicated that soluble solid components, total sugar and deoxidized sugar was reduced with prolong of the fermentation, and mycelium and cordycepin was increased firstly and then reduced. The content of free amino nitrogen was firstly changed slowly and then increased. The crude polysaccharide was reduced a few.