Since the Ad hoc network possesses characteristics including distribution, mobility etc, we propose Hash-chain based Public Key Management Algorithm of Ad hoc network in this work and make comparisons with existing public key management approaches. It has reached the goals of public key distribution, application, maintenance and revocation, and the use of Montgomery Thinking can improve the calculation speed about 41.25%. The innovations of adding of starting time into the certificate and the reuse of the time parameters can effectively avoid the effect of private key leakage and replay attacks, and give the system higher security and better space-time costs. Finally the result of the experiment proves that this is an effective public key management algorithm.