The monitoring methods and research status of friction, frictional heat and frictional vibration and noise in mechanical frictional process were discussed. The mechanism and influencing factors of friction were explained and the presentation focused on the frictional monitoring methods: direct and indirect methods. The theoretical study of analytical and finite element methods was summarized, and the monitoring methods in frictional temperature were emphatically expressed: direct and indirect thermometry. The mechanism of frictional vibration was stated, and the extraction of frictional vibration characteristics was emphatically summed up: time domain, frequency domain method and the time-frequency method. The mechanism of frictional noise was introduced, and the monitoring method of the frictional noise with vibration was described. The future trends of multi-feature and integrated monitoring in mechanical frictional process were pointed out.