Disclosed are a data transmission method and device, used to solve the problem of achieving air interface group calling and multicasting when a base station is connected to a network side via an IP interface; the data transmission method of the present invention comprises: the base station determines a group air interface identifier corresponding to an IP broadcast address or an IP multicast target address; the base station assigns the air interface identifier to a user equipment in the group; and the base station schedules and transmits the air interface data via the air interface identifier.