A multi-screen video playback system includes: a video playback device having a main display to playback a target video; a portable communication device having a screen; and a multi-screen display controlling server configured to operably establish a device group relationship between the video playback device and the portable communication device, to transmit the target video to the video playback device via a network, and to transmit an auxiliary video to the portable communication device via the network. The multi-screen display controlling server receives a notice information generated by the video playback device while the video playback device playbacks the target video, and instructs the portable communication device to begin displaying the auxiliary video on the screen according to the notice information.