To test the transition characteristics of friction state during the start-up and stop stages of contact mechanical seal,the friction characteristics of the C-SiC pairing materials were experimentally studied by using the self-developed friction and wear experimental device.By collecting the acoustic emission (AE) signal and friction torque data during start-up and stop process,the correlation between them was analyzed,and the transformation characteristics of end face friction during start-up and stop process were studied.The results show that the root mean square value of AE signal and friction torque value have the same evolution trend in the start-up and stop stage,which first increases,then decreases,and finally increases to a stable value,showing a strong correlation.The AE signal peak of pairing materials appears at about 7 s,indicating the transition from dry friction state to mixed friction state occurs at this speed.The AE signal and friction torque value in the stable stage are directly proportional to the speed and pressure respectively.