Extract of Cordyceps militaris was added into milk to produce yoghourt. In order to study the effects of extract of Cordyceps militaris on quality of yoghourt, series of indexes including viscosity, color, pH, acidity, water-holding power, the lactic acid bacteria, sensory evaluation and volatile flavor compounds were respectively evaluated during storage of Cordyceps militaris yoghourt. The results showed that extract of Cordyceps militaris could promote the growing of lactic acid bacteria, change the color of yoghourt, enhance the viscosity and water-holding power, and inhibit the increasing of acidity. The yoghurt had the best sensor evaluation when 6% soluble solid content of Cordyceps militaris extracts was added. The relatively percentage of volatile flavor compounds such as acids, ketones and so on in Cordyceps militaris yoghourt was higher than those in regular yoghourt.