Located in the middle and north sections of Changning-Menglian suture zone, Lailitoushan, Yunling and Gengma plutons are mainly composed of monzogranites. The zircon LA-ICP-MS U-Pb dating indicates that the three granitoid plutons intruded simultaneously at about 231 Ma. The three plutons have 65.65%～67.68% SiO₂, with high K₂O (K₂O/Na₂O=2.71%～1.42%) and low CaO ( 1.35%～2.98%). These plutons probably formed in a post-collisional setting, which may imply that the Burma-Thai-Malaysia microcontinent collided with the Simao block before 232 Ma (prior to Late Triassic).