Abstract: A digitized FM (frequency modulation) stereo multiplexing circuit for an FM stereo transmitter has a digital audio I/O interface, a digitized FM stereo multiplexing circuit, a low-pass filter and an FM circuit. When a digital audio data is inputted, a digital audio decoder decodes the digital audio data to acquire left and right channel audio signals. The left and right channel audio signals are inputted to an over-sampling unit circuits to process sampling and then to output to an FM stereo multiplexer. The FM stereo multiplexer then generates a master signal and a secondary signal by processing the sampled left and right channel audio signals. In the meanwhile a switch signal and a pilot signal are acquired with an address counter to output from a memory unit. Then the master signal, the secondary signal and the pilot signal are combined as the digital FM stereo data.