A system comprising a first terminal device and another terminal device with which the terminal device is in communication with, the first terminal device comprising: an acquiring unit, configured to acquire a network resource parameter of a network allowed to be accessed; a determining unit, configured to determine, from the network allowed to be accessed and according to the network resource parameter of the network allowed to be accessed, a target network to be switched to; a sending unit, configured to send the network resource parameter of the determined target network to the other terminal device, and the other terminal device is configured to select, according to the network resource parameter, a communications mode of an application program that is run on the other terminal device, wherein the application program is an application program that needs to use network communications; and a switching unit, configured to switch the first terminal device from a current network to the target network, wherein: the network resource parameter comprises bandwidth, a network charge rate, or network stability, and the determining unit is specifically configured to determine, from the network allowed to be accessed and according to the bandwidth of the network allowed to be accessed, a network with largest bandwidth as the target network to be switched to; or the determining unit is specifically configured to determine, from the network allowed to be accessed and according to the network charge rate of the network allowed to be accessed, a network with a lowest charge as the target network to be switched to; or the determining unit is specifically configured to determine, from the network allowed to be accessed and according to the network stability of the network allowed to be accessed, a network with highest stability as the target network to be switched to. an acquiring unit, configured to acquire a network resource parameter of a network allowed to be accessed; a determining unit, configured to determine, from the network allowed to be accessed and according to the network resource parameter of the network allowed to be accessed, a target network to be switched to; a sending unit, configured to send the network resource parameter of the determined target network to the other terminal device, and the other terminal device is configured to select, according to the network resource parameter, a communications mode of an application program that is run on the other terminal device, wherein the application program is an application program that needs to use network communications; and a switching unit, configured to switch the first terminal device from a current network to the target network, wherein: the network resource parameter comprises bandwidth, a network charge rate, or network stability, and the determining unit is specifically configured to determine, from the network allowed to be accessed and according to the bandwidth of the network allowed to be accessed, a network with largest bandwidth as the target network to be switched to; or the determining unit is specifically configured to determine, from the network allowed to be accessed and according to the network charge rate of the network allowed to be accessed, a network with a lowest charge as the target network to be switched to; or the determining unit is specifically configured to determine, from the network allowed to be accessed and according to the network stability of the network allowed to be accessed, a network with highest stability as the target network to be switched to. the network resource parameter comprises bandwidth, a network charge rate, or network stability, and the determining unit is specifically configured to determine, from the network allowed to be accessed and according to the bandwidth of the network allowed to be accessed, a network with largest bandwidth as the target network to be switched to; or the determining unit is specifically configured to determine, from the network allowed to be accessed and according to the network charge rate of the network allowed to be accessed, a network with a lowest charge as the target network to be switched to; or the determining unit is specifically configured to determine, from the network allowed to be accessed and according to the network stability of the network allowed to be accessed, a network with highest stability as the target network to be switched to.