A method for charging an inter-PLMN roaming data service online, comprising: determining, by a visited-place packet data network gateway, whether a home public land mobile network identifier of the access subscriber is the same as a public land mobile network identifier of the visited-place packet data network gateway, wherein if the home public land mobile network identifier of the access subscriber is different from the public land mobile network identifier of the visited packet data network gateway, the access subscriber is a roaming subscriber; if the access subscriber is a roaming subscriber, establishing, by the visited-place packet data network gateway, an online charging session between the visited-place packet data network gateway and a home online charging system of the access subscriber for the access subscriber; determining, by the visited-place packet data network gateway, whether the online charging session is an inter-PLMN online charging session; and if a determining result indicates yes, forming, by the visited-place packet data network gateway, a first charging information parameter list by using a preconfigured charging information parameter applicable to a roaming subscriber; sending, to the home online charging system by the visited-place packet data network gateway, a first quota request message that carries a rating group, to request the home online charging system to return, according to the rating group, a roaming data service quota authorized by the home online charging system; receiving, by the visited-place packet data network gateway, the roaming data service quota; and sending, by the visited-place packet data network gateway, first charging information to the home online charging system according to the first charging information parameter list, wherein the first charging information comprises a usage of the roaming data service quota. determining, by a visited-place packet data network gateway, whether a home public land mobile network identifier of the access subscriber is the same as a public land mobile network identifier of the visited-place packet data network gateway, wherein if the home public land mobile network identifier of the access subscriber is different from the public land mobile network identifier of the visited packet data network gateway, the access subscriber is a roaming subscriber; if the access subscriber is a roaming subscriber, establishing, by the visited-place packet data network gateway, an online charging session between the visited-place packet data network gateway and a home online charging system of the access subscriber for the access subscriber; determining, by the visited-place packet data network gateway, whether the online charging session is an inter-PLMN online charging session; and if a determining result indicates yes, forming, by the visited-place packet data network gateway, a first charging information parameter list by using a preconfigured charging information parameter applicable to a roaming subscriber; sending, to the home online charging system by the visited-place packet data network gateway, a first quota request message that carries a rating group, to request the home online charging system to return, according to the rating group, a roaming data service quota authorized by the home online charging system; receiving, by the visited-place packet data network gateway, the roaming data service quota; and sending, by the visited-place packet data network gateway, first charging information to the home online charging system according to the first charging information parameter list, wherein the first charging information comprises a usage of the roaming data service quota.