In order to acquire the laser source with stable frequency, introduce a method to use piezoelectric ceramic micro-displacement to regulate laser resonant cavity length. Use D/A card to output non-equidistant regulate voltage sequences to piezoelectric ceramic driving power. Then the piezoelectric ceramic shape is changed to regulate laser resonant cavity length to change averagely. The experimental results show that the length of the laser resonant cavity can be regulated accurately and the frequency of the laser is stability, high positioning accuracy with nm level.