Abstract: Aiming at the characteristic of video stream and the corresponding requirements in real world applications,a novel video stream encryption algorithm is proposed based on chaotic system-EVSBC.This algorithm encrypts and decrypts the digital video stream in frequency domain.In addition,we integrate this algorithm is integrattd into the latest MPEG-4 CODEC.The proposed algorithm makes full use of the features of video.And it can completely satisfy the requirement of video-based applications,while the security can be guaranteed actually.