Abstract: Refrigeration system Pressure vessels are widely used, and there is no reliable real-time dynamic monitoring method for this in-service pressure vessels. The acoustic emission testing technology is proposed for real-time monitoring of the refrigeration system pressure vessel, the fatigue load test is achieved for Q345R steel which is manufacturing materials of the pressure vessels, and characteristic parameter analysis, waveform and spectrum analysis are carried out to the signals collected from the whole material damage process, and then the turning points of material from the crack to fracture failure process are found, and the characteristics of different damage stages of AE signal waveform and spectrum are studied and compared, and the AE signal characteristics of each stage are found out, which can provide a reliable basis for acoustic emission dynamic monitoring and evaluation of Q345R.