Abstract: Abstract：The SHRIMP dating technique was applied to determine the U-Pb ages of zircons from the Yiwulüshan granite, western Liaoning. The zircon samples were fresh and unweathered. The rock is coarse-grained biotite monzogranite. Through accurate measurements three ages were obtained; they are ~2500, 224 and 161 Ma. The upper intercept age of ~2500 Ma is the record of the evolution of the Archean old continental nucleus; the crystallization age of 224 Ma is the record of the Indosinian tectono-thermal event; and the magmatic emplacement age of 161 Ma is the record of orogeny of the main orogenic phase of the Meso-Cenozoic intracontinental orogenic belt in the Yanshan area and also an age when the regional structural regime started transition.