The assembly accuracy of the high precision spindle of vertical CNC lathe directly influences table accuracy, so as to affect parts quality. So adjusting accuracy of spindle is very important. CK5225 series machine tool has high precision, good highspeed stability, high machining precision，getting more and more users favor. One of the most critical parameters of the machine is the high accuracy of the spindle, which radial and end face beatings are strictly controlled in the range of 0005 mm. Through designing assembly process, improving assembly method and manufacturing special tools, the accuracy requirements are guaranteed.