A call switching method, comprising: when a first terminal device detects an input operation that is of initiating a call request to a second terminal device and that is input by a user, or when a first terminal device receives a first call request that is initiated by a second terminal device by using a second-type communications network, detecting, by the first terminal device, whether both the first terminal device and the second terminal device are in a first-type communications network; and when the first terminal device detects that both the first terminal device and the second terminal device are in the first-type communications network, initiating, by the first terminal device, a second call request to the second terminal device by using the first-type communications network, or sending, by the first terminal device, first prompt information to the second terminal device, wherein the first prompt information is used to indicate that both the first terminal device and the second terminal device are in the first-type communications network, and the first-type communications network is different from the second-type communications network, characterized in that when the second call request is a video call request, after the second call request is responded, the method further comprises: determining, by the first terminal device, whether signal quality of the first-type communications network meets a preset condition; when the signal quality of the first-type communications network does not meet the preset condition, initiating, by the first terminal device, a voice call request to the second terminal device by using the second-type communications network; and after the voice call request is responded, sending and receiving, by the first terminal device, audio data of the video call by using the second-type communications network, and sending and receiving image data of the video call by using the first-type communications network. when a first terminal device detects an input operation that is of initiating a call request to a second terminal device and that is input by a user, or when a first terminal device receives a first call request that is initiated by a second terminal device by using a second-type communications network, detecting, by the first terminal device, whether both the first terminal device and the second terminal device are in a first-type communications network; and when the first terminal device detects that both the first terminal device and the second terminal device are in the first-type communications network, initiating, by the first terminal device, a second call request to the second terminal device by using the first-type communications network, or sending, by the first terminal device, first prompt information to the second terminal device, wherein the first prompt information is used to indicate that both the first terminal device and the second terminal device are in the first-type communications network, and the first-type communications network is different from the second-type communications network, characterized in that when the second call request is a video call request, after the second call request is responded, the method further comprises: determining, by the first terminal device, whether signal quality of the first-type communications network meets a preset condition; when the signal quality of the first-type communications network does not meet the preset condition, initiating, by the first terminal device, a voice call request to the second terminal device by using the second-type communications network; and after the voice call request is responded, sending and receiving, by the first terminal device, audio data of the video call by using the second-type communications network, and sending and receiving image data of the video call by using the first-type communications network. determining, by the first terminal device, whether signal quality of the first-type communications network meets a preset condition; when the signal quality of the first-type communications network does not meet the preset condition, initiating, by the first terminal device, a voice call request to the second terminal device by using the second-type communications network; and after the voice call request is responded, sending and receiving, by the first terminal device, audio data of the video call by using the second-type communications network, and sending and receiving image data of the video call by using the first-type communications network.