The present invention relates to a method for assigning a radio resource to a mobile station that requests a data service by collecting radio resources at a constant rate from mobile stations being served by a base station apparatus with a 1xEV-DO system. Especially, the present invention is appropriate for managing radio resources more efficiently and for improving the quality of service, by collecting part of the radio resource assigned to a mobile station having a lower service grade, among other mobile stations in service, assigning the collected radio resource to a mobile station that requested a data service, and providing the data service to the mobile station based on the assigned radio resource.