The invention discloses an embedding method and a detection method for video digital hidden information. The embedding method comprises the steps of: selecting an original video frame image to be embedded with digital hidden information from an original video; converting the digital hidden information to be embedded into a hidden information binary image; performing block DCT (Discrete Cosine Transform) on the original video frame image; modifying an intermediate frequency coefficient of each image sub-block after DCT according to the pixels corresponding to each image sub-block in the hiddeninformation binary image to embed the digital hidden information; performing block inverse discrete cosine transform on the modified DCT coefficients to obtain a video frame image embedded with the digital hidden information; and replacing the original video frame image in the original video with the video frame image embedded with the digital hidden information. The detection method comprises thesteps of: selecting the video frame image embedded with the digital hidden information and a previous frame of image from the video and subtracting the both directly to obtain a difference image; andsuccessively performing down-sampling and binarization on the difference image to obtain a hidden information binary image.