Based on the theoretic analysis of piezoelectric actuator power supply and the adjusting principle of the cavity length of ring laser gyro,a 0~300 V continuous adjustable and computer controlled power supply system driven by piezoelectric crystal has been designed and it has been applied to ring laser gyro automatic mode\|sweep system designed by authors.The mode\|sweep curve obtained by experiment shows that this power supply system can meet the requirement of automatic mode\|sweep system of ring laser gyro.