To meet the requirements of fast search and high precision tracking at ultra-low speed for a 2.5 m wide field telescope， the design method of the three closed-loop control system of position， velocity， and current of telescope main axes AC servo is introduced. Firstly， a sinusoidal signal is injected into the set current closed-loop reference input end， and the speed open-loop frequency characteristic curve of the main axes servo system for the telescope is measured using a frequency sweep. Then， the structural filter is designed according to the resonant frequency to suppress the mechanical resonance so as to achieve a higher closed-loop bandwidth. Finally， according to the identified control model， the speed loop linear active disturbance rejection （LADRC） controller and position loop proportional controller are designed. The velocity loop estimates the disturbance and compensates for its effects based on the linear extended state observer， which achieves higher low-speed tracking accuracy. To solve the fast search problem， the position loop arranges the transition process according to the maximum allowable velocity and acceleration of the device and based on the discrete maximum velocity tracking differentiator. The experimental results show that， compared with the PI control， LADRC reduces the fast step search time of 1.24° FOV for a 2.5 m wide field telescope from 1.6 s to 1.0 s. The equivalent sinusoidal guidance error RMS value decreases from 1.08″ to 0.60″ when tracking the sine curve with a velocity of 2 （°）/s and acceleration of 1 （°）/s²， The steady-state error RMS of position decreases from 0.015 8″ to 0.010 6" when tracking the slope of position at 0.000 1 （°）/s. The experimental results indicate that LADRC can meet the requirements of high efficiency， fast search， and precise tracking at low speed for large field angle telescopes.