Evaluation of hair growth has been always the focus of dermatologists and researchers,which has become increasingly apparent with the wide application of finasteride and minoxidil in the treatment of androgenetic alopecia.The biological parameters of hair growth mainly include hair density,shaft diameter,rate of linear growth.cycle status.The anagen:telogen ratio is the best indicator for cycle status given the impracticalities of measuring the duration of anagen.Up to now,these methods Call be divided into three groups,i.e.,non-invasive,semi-invasive and invasive methods.Also,all methods have their special application range and advantages.