Abstract: Carotenoids are the key factors affecting the formation of fruit bodies of Cordyceps militaris. Three type strains Cordyceps militaris which had typical colony morphology were selected. The influence of conditions such as light and dark cycle, different colony morphology on the formation of the fruit body and contents of carotenoids was investigated. Carotenoids were extracted by hydrochloric acid (HCl) with heating (by boiling water) and detected by absorption spectroscopy. The result was that the strains had ability to product fruit bodies in three morphology differently, the formation of fruit body and colony morphology were not related. The fruit body could not be formed as the carotenoid content of less than 3000μg/g. However, the rate of formation of fruit body was 2, 7, 5 each square centimetre, as the carotenoids contents of 3000³500μg/g, 3500⁶500μg/g, more than 6500μg/g, respectively. On the contrary, neither the fruit body and the carotenoids could be detected under the dark condition.