Neutron transport numerical simulation of different energy of neutron sources is performed in hypothetical nuclear warhead models.Three methods of actively warhead detection are analyzed and the feasibility of actively detecting warheads with three types of neutron sources is studied.With 14.1 MeV pulse neutron source,distribution of delayed neutron flow with time is studied.Results show that the warheads can be detected without exposing the sensitive information of nuclear weapons by detecting the delayed neutrons.