Abstract: The Pilok tin-tungsten mining area is located in the central segment of the west granite belt in Southeast Asia, western Thailand. The precise dating of the granites from the mining area is very important for deep understanding of the crystallization time and tectonic background of this granite belt as well as the regional magmatism-mineralization. The new SHRIMP U-Pb dating results of magmatic zircons in two monzogranite samples from the Pilok tin-tungsten mining area of western Thailand show that their crystallization ages are 181.7±4.8Ma and 175.3±3.3Ma respectively, belonging to the Toarcian period of early Jurassic. Geochemical analyses reveal that the monzogranites are of the high-K calc-alkaline and peraluminous S-type. Combined with regional geological setting, the authors hold that the monzogranites in Pilok mining area should be the products of the Bangonghu-Nujiang-Mogok oceanic crust which subducted beneath the west Tengchong-Tanintharyi continental block.