A method for implementing security of single radio voice call continuity (SRVCC), comprising: after single radio voice call continuity handover, a calling party performing encrypted media stream interaction with a called party through a public switched telephone network media gateway; and the public switched telephone network media gateway encrypting media streams sent to the called party and decrypting the encrypted media streams sent from the called party; wherein, encryption keys in the public switched telephone network media gateway come from an enhanced mobile switch center; wherein, in the step of the public switched telephone network media gateway encrypting media streams sent to the called party and decrypting the encrypted media streams sent from the called party, the public switched telephone network media gateway uses a first key to encrypt the media streams sent to the called party, and uses a second key to decrypt the media streams sent from the called party; wherein, the first key is generated by the enhanced mobile switch center and notified to the public switched telephone network media gateway, and the second key is generated by the called party and notified to the public switched telephone network media gateway; wherein, a mode of the public switched telephone network media gateway acquiring the first key and the second key is: after the single radio voice call continuity handover, the enhanced mobile switch center generating the first key, adding a key attribute in session description protocol information sent to the called party, and carrying the first key in the key attribute; the called party generating the second key, adding a key attribute in session description protocol information sent to the enhanced mobile switch center, and carrying the second key in the key attribute. after single radio voice call continuity handover, a calling party performing encrypted media stream interaction with a called party through a public switched telephone network media gateway; and the public switched telephone network media gateway encrypting media streams sent to the called party and decrypting the encrypted media streams sent from the called party; wherein, encryption keys in the public switched telephone network media gateway come from an enhanced mobile switch center; wherein, in the step of the public switched telephone network media gateway encrypting media streams sent to the called party and decrypting the encrypted media streams sent from the called party, the public switched telephone network media gateway uses a first key to encrypt the media streams sent to the called party, and uses a second key to decrypt the media streams sent from the called party; wherein, the first key is generated by the enhanced mobile switch center and notified to the public switched telephone network media gateway, and the second key is generated by the called party and notified to the public switched telephone network media gateway; wherein, a mode of the public switched telephone network media gateway acquiring the first key and the second key is: after the single radio voice call continuity handover, the enhanced mobile switch center generating the first key, adding a key attribute in session description protocol information sent to the called party, and carrying the first key in the key attribute; the called party generating the second key, adding a key attribute in session description protocol information sent to the enhanced mobile switch center, and carrying the second key in the key attribute.