A multimedia data line convenient for low-speed signal transmission comprises a sending end and a receiving end, wherein the sending end is provided with a sending end proxy module, and the receivingend is provided with a receiving end proxy module. The proxy module is respectively connected with the low-speed signals at the two ends to recombine the received low-speed signals which are transmitted to the receiving end proxy module through the private protocol information, or restore the received private protocol information into a low-speed signal format. A proxy is introduced in multimedialow-speed signal transmission, and information is transmitted through a private protocol in the proxy modules of the sending end and the receiving end. In this way, the number of transmission channelscan be reduced, and the cost of the cables can be lowered. When long-distance transmission is carried out, the HDCP and the SCDC are supported, and the I2C standard is met, and I2C clock stretching is supported. The operation is easy. The transmission medium is not limited to optical transmission, and the transmission medium range is expanded.