Zircons collected from Hanfang intrusions in Ganxian, Jiangxi Province, whose weathered crust produced many rare earth element(REE) deposits, have been dated by using Laser Ablation-Multicollector Inductively Coupled Plasma-Mass Spectrometry(LA-MC-ICPMS) and are presented in this paper. The dating results from typical magmatic zircons with good shape and oscillatory zoning show that the coarse-grained biotite monzonitic granite intruded in the Caledonian era, during the convergence between Yangtze block and Cathaysia block, and the fine-grained biotite monzonitic granite intruded in the early Yanshan epoch as the results of lithospheric thinning and delamination during subduction of the old Pacific plate to the South China Plate.