Embodiments of the present invention disclose a method for data transmission, which is used to increase resource utilization. The method according to the embodiments of the present invention includes: receiving, by a media processing device, a service request sent by a user equipment, where the media processing device is located at a radio access network where the user equipment is located; obtaining, by the media processing device, service data corresponding to the service request; obtaining, by the media processing device, air interface resource information of a cell where the user equipment is located and transmission resource information; and performing, by the media processing device, content adaptation and bit rate selection on the service data according to the obtained air interface resource information and transmission resource information. The embodiments of the present invention further disclose a system and a relevant device for data transmission.