Abstract: Key management schemes based on threshold mechanism can provide high security, but lower certificate success rate and bad scalability; key management schemes based on certification chain satisfy self-organized features, but their security depends on trust degree of nodes and could not be applied high security environment. We advance hybrid key management scheme based on threshold mechanism and certification chain. Simulation shows that with less increment of communication overhead, our scheme can improve both certificate success rate and system security and better balances security and availability, and satisfies security needs of Ad hoc networks.