According to the high quality demand of machine tool spindle dynamic balancing, on the basis of quantitative comparison for two traditional balancing methods, an improved high precision balancing method was proposed, that is, precise targeting method. A vertical and a horizontal rotor test rig were built to test and verify those methods. For the widespread use of the measured phase balancing method and the measured amplitude balancing method, the whole circumference of trial weight test were done on the two test rigs, the stability and accuracy of those two methods were quantitatively analyzed, and then, the precise targeting method was proposed based on the improved measured phase balancing method. Through no more than two times of trial weight, the method can determine the position of optimal trial weight quickly and reliably, and obtain the initial unbalance accurately, which can improve the dynamic balancing precision obviously