Abstract: The Luang Prabang tectonic belt in Laos is located in the western of Indo-China Plate, and it is one of the important tectonic belts in Southeast Asia-Tethys domain. Multi-stage magmatic activities in this area recorded multi-stage tectonic-magmatic evolutions. However, there are few reports on magmatic activity related to the closure process of Paleo-Tethys Ocean, thus the relationship of tectonic evolution-magmatism-metallogenesis in the process remain controversial. Based on field geological observations and petrographic studies, this article carried out zircon U-Pb LA-ICP-MS dating of quartz diorite in Luang Prabang, Laos. The results show that the crystalline age of the quartz diorite is 260.5±1.8 Ma, indicating a Middle-Late Permian magmatic activity in the Luang Prabang tectonic belt. Combine with previous studies, we believe the medium-acid intrusive rock is likely to be the product of magmatic activity during the eastward subduction of the Paleo-Tethys Ocean-plate and closure of the Nan-Sra Kaeo backarc basin. It also provides new data indicating that the Luang Prabang tectonic zone may link to the Nan-Uttaradit to the south.