A speech transmission system was designed to conquer the restriction of analog communication system in coal mine. After compressed by multi-band excitation, the voice data was transmitted on CAN (controller area network)-bus to achieve long transmission distance at low speed. Compared simulation data and experimental data, it got the result that CAN-bus can bare the speech data after MBE coding compression, and the composing of system voice is perfect and understandable, with the distortion of voice signal les15%, voice intensity les90 dB after magnified, and suitable for voice transmission in coal mine.