Disclosed are a device and method for displaying a video over a network, the method includes: determining a first resolution of a target video frame input over network, and comparing the first resolution with a screen resolution of a mobile terminal, and the first resolution with a resolution of a video frame displayed by the mobile terminal; if the first resolution is different from the screen resolution of the mobile terminal, determining a first ratio of a row resolution of the screen resolution to a row resolution of the first resolution, and a second ratio of a column resolution of the screen resolution to a column resolution of the first resolution; determining the size of a display window according to the smaller one of the first ratio and the second ratio, which is a display scale, and the first resolution; and displaying the target video frame in the display window.