Cytochrome c has been proved to be a powerful scavenger of O2·- and H2O2, the ferricytochrome c scavenges O2·- and the ferrocytochrome c scavenges H2O2. As the respiratory chain leak some electrons from complex Ⅰ and Ⅲ to generate O2·- and then O2·- dismutate to H2O2,the scavenge of O2·- and H2O2 by cytochrome c makes respiratory chain operated with two electron leak bypass. Cytochrome c plays a role to keep O2·- and H2O2 in the normal physiological level in mitochondria. A concept of radical metabolism is introduced into mitochondria based on the electron leak bypass is the metabolic path of O2·-. The role of electron leak of respiratory chain in cell apoptosis is discussed in the dysfunction of radical metabolism of mitochondria.