Laser tracker has the advantages of high precision, real-time, dynamic and easy to be moved etc. The site calibration and accuracy testing of the laser tracker are very necessary in actual measurement. The error of fixed points and the plane error of standard granite set square was measured by the LT300 laser tracker in order to verify the precision of the laser tracker. The relationship between measuring accuracy and distance can be found by changing the angle and distance between set square and the laser tracker. So the measuring accuracy of the LT300 laser tracker was obtained on the actual location.