The present invention relates to a method for realizing a secure forking call session, which comprises: performing authentication between a calling party and a KMS or between each called party and the KMS, and acquiring a shared key between the calling party and the KMS or a shared key between each called party and the KMS; generating a random number by the calling party and calling each called party through an IMS; generating a random number by each called party and acquiring a media root key from the KMS; generating a media key, which is shared with the calling party, by each called party according to the media root key and the random number generated by the called party; sending the media root key and the generated random number by a called response party in the called parties, who responds the call, to the calling party through the IMS network; generating a media key identical to that of the called response party by the calling party according to the media root key and the random number generated by the called response party; and performing a secure media session between the calling party and the called response party with the identical media key.