An inline holographic digital watermark technology using quick response code (QR code) as watermark was put forward. The algorithm used QR code as watermark to improve robustness; the watermark was encrypted by double random phase encryption technology to enhance security. The encrypted watermark embedded into the medium frequency by using discrete wavelet transform which could take both invisibility and robustness into account. In watermark extraction, Gaussian filter enhanced recognition and decoding of the QR code. Experiments showed that the algorithm has good invisibility, security, and robustness.