The quick change tool post is a main accessory of the machine tool, it consists of tool post and many kinds of tool holders, according to the processing requirements of the workpieces, corresponding tool holders are selected to finish cylindrical facing, end facing, cutting, drilling, reaming, boring as well as other processing. It realizes to mount tool outside the machine tool, it has exchange tool quickly, high accuracy, strong rigidity etc. It is satisfactory accessories in place of square turrets.