The invention discloses a method for converting video fields, which comprises the steps as following: receiving a video source file; obtaining the resolution ratio of an output target; judging the frame scanning mode of the video source file; isolating the odd rows and the even rows of each frame of the video source file if the video source file is an interstage scanning file, and converting all odd rows and even rows of the video source file into the resolution ratio of the output target; converting the resolution ratio of the video source file into the resolution ratio of the output target if the video source file is a non-interlaced scanning file; and extracting the output of the odd rows and the even rows as the video fields. By adopting the method for converting the video fields, the working time is greatly shortened, the working cost is lowered, and the output quality of image is ensured.