A method for making a terminating network domain selection, applied in a network system including a CS network and an IMS. The method includes: receiving an IMS service request destined to a served user; judging whether the service request is appropriate to be delivered to the CS network according to a service category of the IMS service request, making a terminating network domain selection according to terminating network domain selection related factors and performing subsequent delivering processes according to the determination of the terminating network domain selection if determining that the IMS service request is appropriate to be delivered to the CS network. The present disclosure also discloses a communication apparatus and a network system.