To solve the singleness of audio broadcasting of the early warning information,a pre-processing system of DMB(Digital Multimedia Broadcasting) early warning information based on rate control was designed according to the study of DMB standards.The audio and video of the warning information were encoded by the algorithm of MPEG-4 HE AAC and H.264/AVC and synthesized into transport streams in this system firstly.Then in order to improve communication reliability,the transport streams were error corrected by Reed Solomon encoding and convolutional interleaving.Meanwhile,to solve the problem of the transmission instability rate and ensure the value of the rate to be constant,a transportation control method of audio and video matching control based on rate control is proposed.Through this method,the intelligent controlling of the output rate is realized by adopting inserting null packages.The whole system is validated by experiments and outperforms former DMB preprocessing system in both reliability and stability.