In consideration of the fact that previous age data of the old rocks in southern Jilin were somewhat too young, and there is some confusion concerning the boundary between the Archaean and the Proterozoic Eon, this paper, by using the Sm-Nd isochron and zircon U-Pb dating methods, divides the metamorphic rocks in this region into 4 intervals: the pre-Fuping cycle (before 2600 Ma), the first phase (2600-2500 Ma) , the second phase (2500-2400 Ma) and the third phase (2400-2350 Ma) of the Fuping cycle. The third phase is classified into the Archaean and acting as the boundary between the Archaean and the Proterozoic. When the tectonic setting of the southern Jilin old land turned from active to stable, there occurred alternation of the trench-arc-basin system in the new and old plates, as well as crustal uplift and erosion, which resulted in the younger K-Ar ages. Therefore, to include the transitional tectonic setting and the geologic events occurring in the interval 2400 - 2350 Ma into the Archaean will be helpful to our understanding of the crustal evolution of this region, and the formation of the Banshigou greenstone belt iron deposit and the Jiapigou shear zone gold deposit.