A method for charging an inter-Public Land Mobile Network (PLMN) roaming data service online, and a device are presented. The method includes, after determining that an access subscriber is a roaming subscriber, establishing, by a visited-place packet data network gateway, an online charging session for the access subscriber; determining a first charging information parameter list; sending, to a home online charging system, a first quota request message carrying a rating group; receiving a roaming data service quota of the rating group sent by the home online charging system; and sending first charging information to the home online charging system according to the first charging information parameter list. The disclosed embodiments can simplify a network connection between a visited-place Packet Data Network Gateways (PGW) and an Online Charging System (OCS) of another operator that has a roaming agreement with the visited-place operator, reduce network connection complexity, and improve network connection efficiency.