The Anjishan pluton in Ningzhen area(i.e. Nanjing—Zhenjiang area) is the earliest conformed to be adakitic rocks in the Middle and Lower Yangtze Valley. For further understanding its petrogenesis and the deep geological evolution, we did geochronology using zircon LA ICPMS U Pb dating for the granodiorite porphyry from Anjishan pluton. A weighted mean 206Pb/235U age of 108.8±1.2 Ma is obtained, which represent magma intrusive age of Early Cretaceous. In addition, the refined geochronological framework of the Mesozoic magmatic rocks in the Middle and Lower Yangtze Valley is established by combining with the expressed high precision data of ages. It can be divided into four stages, namely 148~133 Ma (the first stage), 131~127 Ma (the second stage), 126~123 Ma (the third stage) and 109~102 Ma (the fourth stage).