The star as calibrate source has advantages of stable position and stable radiation.To get the long period data,an earth-based observing star system was designed,and it can realize the long period tracking and scanning for star.The position of star is gotten by calculating the star’s trajectory;the tracking trajectory of the equatorial is determined to promise that the target star is always in the view of the optical spectrometer.Observing the target star by the optical spectrometer,the result of observation can be gotten.The maximum error which the experiment requires is 0.01°,while the tracking accuracy of the system gotten in the outfield experiment is 0.004°.This proves that the stability and the accuracy of the system can meet the requirement of the experiment,and the facility can track and observe star in high-accuracy.Finally,the error sources of the environment are analyzed.