With the popularity of the worldwide Internet service, IP Video transmission as one of the most important service on Internet has caught the whole world attention to broadly. However, the security problems become the biggest obstacle that the development of VoIP technology has to face,which seriously limit the extensive application of multimedia transfer.Firstly, the design of the Digital Video Transmission system is studied in this paper. To the characteristic of the Video transmission, the Davinci technology that optimizes the digital multimedia transfer is used and the secure SIP protocol is implemented on the ARM926EJ-S of double kernel Davinci. To encrypt the RTP package, a DSP Encrypting subsystem is used. After the design, we discuss the characteristic of the SIP difference from H.323 protocol such as complexity, reliability, and expansibility. Then we introduce the advantages of SIP transfer in architecture, format, function and analyze the secure problem exist in the SIP protocol. By studying the mature SIP scheme and finding out its deficiency, we form a secure scheme based on the PKI and jump encryption in this article and make a comprehensive analysis to the scheme. Last, based on those study, we finish the module design of the secure SIP transmission system and the coding, debugging of SPI device driver that is used to communicate with DSP Encrypting subsystem.