An embodiment of the invention provides a method for guaranteeing QoS of services in a broadband access network includes: establishing a plurality of logical channels between a plurality of subscriber access devices and a Broadband Access Server (BAS) respectively, allocating bandwidth resources for each of the plurality of logical channels; determining whether to allow a real-time service to access the broadband access network according to bandwidth resources occupation information of the plurality of logical channels. Embodiments of the invention provides a broadband access network and device for guaranteeing QoS of services as well.