A service data transmission method, applied to a terminal, comprising: when it is detected that the terminal roams from a local place to a foreign place, requesting and acquiring Virtual-Subscriber Identity Module, V-SIM, card information about the foreign place from a V-SIM card server; disconnecting a network connection that has been established using a Subscriber Identity Module, SIM card, and establishing a network connection using the acquired V-SIM card information; and transmitting service data using the established network connection; characterized in that the method further comprises: when service data are transmitted using the established network connection, gathering statistics on Internet traffic; periodically reporting the statistically gathered Internet traffic to a comprehensive charging server; when the comprehensive charging server calculates according to the reported Internet traffic that a user of the terminal has a remaining amount of data traffic to use and the V-SIM card has no remaining amount of data traffic to use, receiving a release message sent by the comprehensive charging server and releasing the acquired V-SIM card information; establishing a foreign network connection using reacquired V-SIM card information; when the comprehensive charging server calculates according to the reported Internet traffic that the user of the terminal has no remaining amount of data traffic to use, receiving a release message sent by the comprehensive charging server and releasing the acquired V-SIM card information; after the comprehensive charging server recovers the V-SIM card information, disconnecting the established foreign network connection. when it is detected that the terminal roams from a local place to a foreign place, requesting and acquiring Virtual-Subscriber Identity Module, V-SIM, card information about the foreign place from a V-SIM card server; disconnecting a network connection that has been established using a Subscriber Identity Module, SIM card, and establishing a network connection using the acquired V-SIM card information; and transmitting service data using the established network connection; characterized in that the method further comprises: when service data are transmitted using the established network connection, gathering statistics on Internet traffic; periodically reporting the statistically gathered Internet traffic to a comprehensive charging server; when the comprehensive charging server calculates according to the reported Internet traffic that a user of the terminal has a remaining amount of data traffic to use and the V-SIM card has no remaining amount of data traffic to use, receiving a release message sent by the comprehensive charging server and releasing the acquired V-SIM card information; establishing a foreign network connection using reacquired V-SIM card information; when the comprehensive charging server calculates according to the reported Internet traffic that the user of the terminal has no remaining amount of data traffic to use, receiving a release message sent by the comprehensive charging server and releasing the acquired V-SIM card information; after the comprehensive charging server recovers the V-SIM card information, disconnecting the established foreign network connection. when service data are transmitted using the established network connection, gathering statistics on Internet traffic; periodically reporting the statistically gathered Internet traffic to a comprehensive charging server; when the comprehensive charging server calculates according to the reported Internet traffic that a user of the terminal has a remaining amount of data traffic to use and the V-SIM card has no remaining amount of data traffic to use, receiving a release message sent by the comprehensive charging server and releasing the acquired V-SIM card information; establishing a foreign network connection using reacquired V-SIM card information; when the comprehensive charging server calculates according to the reported Internet traffic that the user of the terminal has no remaining amount of data traffic to use, receiving a release message sent by the comprehensive charging server and releasing the acquired V-SIM card information; after the comprehensive charging server recovers the V-SIM card information, disconnecting the established foreign network connection.