A display system comprising a video signal supplier supplying a video signal with a first video signal standard comprising a predetermined sync signal and a data range; a display apparatus supporting one of the first video signal standard and a second video signal standard comprising a sync signal and a data range which are at least being partially different to the first video signal standard and a data range being equal to the first video signal standard and outputting the video signal from the video signal supplier; a selector selecting the display apparatus supporting one of the first video signal standard and the second video signal standard; and a sync signal converter receiving a sync signal in the video signal from the video signal supplier according to a selection of the selector and converts the received sync signal into either the first video signal standard or the second video signal standard, which the selected display apparatus supports, to output the selected display apparatus. With this configuration, the present invention provides a display system which can alternatively select a video signal of one of a first video signal standard and a second video signal standard, which have a different sync signal standard, to output according to a selection of a user and a method of converting a sync signal thereof.