Along with 21st century approaching, the computer and the digitized network technology development has brought the new challenge to the traditional communication way, it no longer was old face-to-face chat, but must carry on the exchange through the network. Through the study of vc++. net tool application, I am familiar with and understand the basic principle of voice transmission, and research the basic process of voice transmission: Gathering, voice compressing, transmitting, decompressing, playback and so on. This system may realize the transmission of voice and text between the local area network, also it can broadcast, in another word, one user can transmit the voice and text to many users simultaneously. It can increase and delete the user, control the volume, preserve and eliminate the record, it may also set the parameter.