This paper is about Simulink QAM modulation and demodulation implementation. Firstly, the basic principle of QAM modulation and demodulation system is introduced. Then, the basic operation of system modeling and simulation under simulation software Simulink is introduced. The emphasis is on modeling and simulation of 16QAM system modules, and 16QAM modulation and demodulation are realized. Finally, a 2DPSK system simulation is carried out to compare it with the 16QAM system. It is concluded that 16QAM is a relatively superior modulation and demodulation system.