Abstract: The northern Liaoning is located in two secondary tectonic units of North China Craton and Paleozoic depression zone in northern margin of North China, with strong late tectonic magmatic activities, especially Jurassic magmatic activity is most intense, when different types of granites were widely developed.However, the formation times of the Mesozoic tonalite in this area is lack of depth research.When carrying out the 1:50 000 regional geological survey, the quartz diorite samples have been collected to carry out the LA-ICP-MS dating. The obtained U-Pb ages of zircons are (173+0.88) Ma (MSWD=5.8), which is in a certain error range. Based on the CL images of these zircons, the formation age of Mesozoic quartz diorite in this area has been restrained precisely. According to the previous results, the formation age of this quartz diorite has been defined as Middle Jurassic. This achievement provides a new chronology evidence for studying the magmatism and tectonic evolution of northern Liaoning.