Abstract: Demon spectrum is one of the characters of ship radiated noise.It can be used as an important basis in target identification.Target identification could be improved if ocean channel's effects on Demon spectrum propagation can be forecasted quickly.The method of quickly forecasting the effects of ocean channel on Demon spectrum is proposed and analyzed theoretically.Changes of Demon spectrum verses receiving distance in some typical channels are calculated.Effects of sound profile,waterbed parameters,depth of source and receiver on Demon spectrum propagation are analyzed.