Temperature rise of highspeed grinding spindle has an important impact on machining accuracy and service life of the electric spindle. The SPM170 highspeed grinding spindle was taken for the study object. Cooling system of the highspeed grinding spindle improvements was studied by using the method of theoretical analysis plus test certifying. It was known by analyzing that the heat was generated mainly of the electric spindle motor by the iron core loss, and the heat of motor part could be effectively removed by the cooling system, which led the electric spindle temperature decrease. The new spiral waterways were designed of SPM170 highspeed grinding spindle cooling system for its improvements and upgrade. The results show that after improvement of the spiral waterway cooling device, the temeperature rise of electric spindle is reduced for about 10 ℃, for which is effectively controlled.