A method for ciphering/deciphering the video data is characterized in that the ciphering component is embedded in the encoding process and adopts a strategy of grouping scrambling for ciphering the DCT coefficient of the digital video data. The deciphering data is embedded into the decoding process and adopts an inverse scrambling strategy which is reverse to the ciphering for deciphering the DCT coefficient of the digital video data. The frame movement compensating of the digital video can be simultaneously executed with scrambling to obtain a higher security. The invention embeds the ciphering/deciphering into the coding/decoding process and has the advantages of high ciphering speed and low actualizing difficulty. The technique of dynamic key is adopted and the invention has strong clear text attacking resistance. The effect of the ciphering/deciphering method of the invention is reduced to the minimum. The quality of the deciphered vide image does not have any loss compared with the video image before ciphering.