Abstract: On the basis of carefully studiying on isotopic dating in the western part of the North Qilian Mountains, a lot of valuable isotopic data which could be considered as representatives were selected. It is concluded from these data that the general research degree is low in isotopic dating and that they are of great significance both in the determination of ages of all the geologic bodies concerned and in the settling upon of the ages of stratum and ore-forming and geologic hot events which have been quarreled in geologic scientific research,ore prospecting and regional geologic survey for a long time.