Rotor imbalance is an important cause of helicopter vibration. The traditional rotor balancing adjustment is a periodic maintenance method， which takes a long time and cannot maintain the vibration level after maintenance for a long time. Therefore， an in light tuning （IFT） system based on smart pitch rod is developed， which can control the length of smart pitch rods according to the digital command sent by the computer， realize the variable pitch input of blade， and then complete the rotor dynamic balance adjustment. It is found that the influence of the displacement of the smart pitch rod end on the rotation frequency vibration component is linear. Thus the adjustment coefficient matrix of smart pitch rod is determined. When the rotor unbalance vibration information is obtained， the corresponding rod is selected as the regulator according to the phase， the adjustment strategy is designed according to the relationship between the amplitude projection in the adjustment vector direction， and the displacement required for the tie rod to complete the balance adjustment is obtained. The effectiveness of this method is verified by rotor tower test. The results show that this method can reduce the rotor vibration level in real time during helicopter flight， and improve rotor dynamic balance adjustment efficiency.