This paper mainly introduces a system which transplanted FFT algorithm into MCU to analyze and process the digital audio signal so as to make realtime display and sound output of music spectrum come true. The hardware part of the system consists of audio input, singlechip analogdigital conversion, dotmatrix unit composed of LED and sound signal amplification output circuit. Using highperformance singlechip STC12C5A60S2 comes with A/D conversion function, the first audio signal is converted to digital signals, and then write the program for FFT operation. Output processing results lighting LED matrix and complete spectrum display. The brightness of the LED is determined by the frequency of the music. Amplifying the input audio signal through the LM386 op amp chip and the external circuit, then output it by the speaker or an external speaker. The design not only has a high practical value and ornamental, and hardware circuit structure is simple. Development and production cost low.