A method for transmitting a man-machine operation picture, a mobile video device thereof, and a video system using the same are provided, which are applicable to a first mobile video device and a second mobile video device wirelessly connected to each other, and the first mobile video device includes a first screen. A display picture data is obtained from a video buffer of the first screen. The first screen displays a first picture according to the display picture data. The first mobile video device converts the display picture data into a video data compliant to a video format, and transfers the video data to the second mobile video device according to a video communication protocol. The second mobile video device displays a second picture according to the received video data, and a displaying content of the second picture substantially includes a displaying content of the first picture.