According to the DCT distribution of the intra frame in H.264, we propose a low bit-rate H.264-based video content protection scheme using watermarking technique. By introducing the idea of sign coding, we embed the watermark into the DCT coefficients by modifying the signs of them. The detection process is blind-which give it an advantage over most existing algorithms. Experiment results show that the embedded water- marks can resist the well known H.264 compression attacks. The proposed scheme produces very few distortions into the video content and can be used for copyright protection applications.