Disclosed is a method for providing a pay-TV service based on a session key. The method includes the steps of: selecting a desired pay event using a program guide displayed on a system of the subscriber and achieving a subscriber private key; filling out a service application based on service information, signing the service application based on a digital signature scheme and encrypting the digital signed service application; transmitting the encrypted service application to a broadcasting station and waiting a response of the broadcasting station; receiving a session key and a subscription authority message from the broadcasting station, decrypting the session key and the subscription authority message and verifying the digital signature; decrypting a channel key, achieving a control word, descrambling event audio/video streams and watching the event; and if the event is terminated or the session key is not effective, stopping watching the event and deleting the session key.