A method and system for deleting a floor in a PoC system is provided, in which a session management server has a function to reset a floor management list, namely to cancel all reserved floors at once, and when an arbitrary PoC user makes a request to reset the floor, the floor is reset according to whether authentication is made the system includes a PoC client attempting to make a request to delete a reserved floor, and a session management server receiving the floor deletion request message from the PoC client and deleting the reserved floor. The method includes making, by a PoC client belonging to an arbitrary group, a request to delete a floor reserved in a floor management list to a session management server, and deleting, by the session management server, the reserved floor when receiving the floor deletion request message from the PoC client.