The embodiment of the invention provides a multi-terminal same-screen-display system and method. In one embodiment, the multi-terminal same-screen-display system comprises a sharing sending terminal, an adapter and a sharing receiving terminal. The adapter can be connected with the sharing sending terminal through an external interface of the sharing sending terminal; the sharing sending terminal is used for detecting whether a same-screen application program is installed in the sharing sending terminal or not when the adapter is inserted into the external interface of the sharing sending terminal, and when it is detected that the same-screen application program is not installed in the sharing sending terminal, an installation package of the same-screen application program is obtained from the adapter to install the same-screen application program at the sharing sending terminal; the adapter is used for selecting at least one monitored sharing receiving terminal for pairing connection after receiving a pairing order for pairing conducted with the sharing receiving terminal, so that screen data of the sharing sending terminal is transmitted to the pairing-connection sharing receiving terminal, and same-screen displaying between the sharing sending terminal and the sharing receiving terminal is achieved.