The present invention relates to a method and a system for providing a sponsored service on an IMS-based mobile communication network, and comprises the steps of: a sponsored service client transmitting to a sponsored service server a sponsored service start request message; the sponsored service server determining the validity of the sponsored service after receiving the start request message; transmitting to the sponsored service client a sponsored service start acceptance message when the sponsored service server determines the sponsored service as valid; generating a sponsored service between the sponsored service client and an Internet service provider server; the sponsored service server generating charged fee information and transmitting the charged fee information to an authentication/authorization/accounting (AAA) server, when the sponsored service client requests termination of the sponsored service; and terminating the sponsored service session. According to the present invention, the sponsored service, in which a third paπy Internet service provider can pay the cost using the mobile communication network instead of a wireless user equipment subscriber, can be provided, and the quality of the service can be dynamically controlled from the point the Internet service is provided.