The invention relates to a display device and a phase detection method thereof. The display device comprises an analog to digital conversion module, a phase position detection module and a time generation module. The analog to digital conversion module is used for receiving a first analog image signal and converting the first analog image signal into a digital signal according to a time signal, wherein first analog image signal comprises first synchronizing information and first image information; the phase position detection module is used for receiving the digital signal and outputting a phase position regulating signal according to a part, corresponding to the first synchronizing information, of the digital signal; and the time generation module is used for outputting the time signal according to the phase position regulating signal.