A display system (100,200,300) capable of displaying a picture-in-picture image, comprising: a first computer (10,1 0a,10c) comprising: a first processor(CPUl); and a first memory coupled to the first processor (10, 10a, 10c), comprising: a first software package; and at least one first application program (PG1,PG2) controlled by the first processor through the first software package; a display device coupled to the first computer (10,10a,10c) and configured to display an image; a second computer coupled to the display device, comprising: a second processor; and a second memory coupled to the second processor, comprising: a second software package; and at least one second application program controlled by the second processor through the second software package; a control device that is an input device for inputting external signals; and a multiplexer selectively coupling the control device to either the first computer (10,10a,10c) or to the second computer; wherein when the first computer (10, 10a, 10c) is triggered by a hotkey, the first processor, via the at least one first application program (PG1,PG2) and the multiplexer through the first software package, drives the display device to display the image, the image displayed on the display device comprises a first image displayed under a full-screen display mode corresponding to the first computer (10,10a,10c) and a second image corresponding to the control device, the first image remains in the full-screen display mode, and the second image is stacked on the first image; wherein, when the first computer (10, 10a, 10c) is triggered by the hotkey, when the control device is linked to the second computer through the multiplexer, the first image corresponding to the first computer is a background image, the second image corresponding to the control device is a control interface image for adjusting media parameters of the display device; wherein furthermore when the first computer (10, 10a, 10c) is triggered by a hotkey, the first processor generates a notification signal to the second computer and the display device, after the notification signal is received by the second computer, the control interface image is generated by the second computer, the control interface image is transmitted and then displayed on the display device, and the control interface image is operated by the control device. a first computer (10,1 0a,10c) comprising: a first processor(CPUl); and a first memory coupled to the first processor (10, 10a, 10c), comprising: a first software package; and at least one first application program (PG1,PG2) controlled by the first processor through the first software package; a first processor(CPUl); and a first memory coupled to the first processor (10, 10a, 10c), comprising: a first software package; and at least one first application program (PG1,PG2) controlled by the first processor through the first software package; a first software package; and at least one first application program (PG1,PG2) controlled by the first processor through the first software package; a display device coupled to the first computer (10,10a,10c) and configured to display an image; a second computer coupled to the display device, comprising: a second processor; and a second memory coupled to the second processor, comprising: a second software package; and at least one second application program controlled by the second processor through the second software package; a second processor; and a second memory coupled to the second processor, comprising: a second software package; and at least one second application program controlled by the second processor through the second software package; a second software package; and at least one second application program controlled by the second processor through the second software package; a control device that is an input device for inputting external signals; and a multiplexer selectively coupling the control device to either the first computer (10,10a,10c) or to the second computer; wherein when the first computer (10, 10a, 10c) is triggered by a hotkey, the first processor, via the at least one first application program (PG1,PG2) and the multiplexer through the first software package, drives the display device to display the image, the image displayed on the display device comprises a first image displayed under a full-screen display mode corresponding to the first computer (10,10a,10c) and a second image corresponding to the control device, the first image remains in the full-screen display mode, and the second image is stacked on the first image; wherein, when the first computer (10, 10a, 10c) is triggered by the hotkey, when the control device is linked to the second computer through the multiplexer, the first image corresponding to the first computer is a background image, the second image corresponding to the control device is a control interface image for adjusting media parameters of the display device; wherein furthermore when the first computer (10, 10a, 10c) is triggered by a hotkey, the first processor generates a notification signal to the second computer and the display device, after the notification signal is received by the second computer, the control interface image is generated by the second computer, the control interface image is transmitted and then displayed on the display device, and the control interface image is operated by the control device.