The self-mixing interference caused by the vibration of piezoceramics was experimentally observed and measured below 2 kHz.The optical feedback strength factor C changes with the vibration frequency of piezoceramics,when the light path and laser drive current are constant.This phenomenon was theoretically analyzed.The optical feedback strength factor C and the spectral width enhancement factor α were also measured.The results validate that the factor α causes the change of C at the different vibration frequency of piezoceramics.