A data transmission system includes a device and a base. The base includes a near field communication (NFC) module and a processing module configured to determine whether a wireless network exits. The NFC module includes a determining unit configured to determine whether the NFC module writes a predetermined tag after the processing module determines the wireless network exits and configured to determine whether the predetermined tag is an authorization code, a sending unit configured to send a service set identifier (SSID) and a password to the device after the predetermined tag is the authorization code, and a control unit configured to switch an input mode of the base to a wireless network mode after the SSID and the password are sent to the device. The device is configured to be connected to the wireless network after receiving the SSID and the password. A communication method is also provided.