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).