In this study, a perceptual encryption algorithm is proposed for H.264/AVC video to enhance the scrambling effect and encryption space. Six new scan orders are designed for H.264/AVC encoder by analysing the energy distribution of discrete cosine transform coefficients. They are proven to have similar performance as the conventional zigzag scan order and its symmetrical scan order. These six new scan orders are combined with two existing scan orders to design a scan-order based perceptual encryption algorithm. Specifically, video encryption is achieved more specifically by randomly selecting one scan order from the eight scan orders with a security key, and the sign bit flipping of DC coefficients is also incorporated to further increase the encryption space. Experimental results show that the proposed approach has the advantages of both low bitrate increase and low computational cost. Furthermore, it is more flexible and has stronger security than the existing scan-order based video encryption schemes.