Abstract: The Precambrian granite rock in Yulongtan region is composed ofmonzonitic granite, quartz syenite and yenogranite.The LA-MC-ICP-MA ages of this granite rockare (502.1+1.7)Ma and (492.7+1.9)Ma. This granite rocks show the geochemical characteristic of aluminum and potassium (K₂O>Na₂O), belonging to the calc-alkaline series.Tectonic environment discrimination shows that this granite rock was formed in the syn-collision tectonic environment.After comprehensively analyzing the related geological data, it is concluded that the Cambrian granite should be formed in the expansion phase of the basin in the south, and caused by the melting of the continental crust in the north when the Langshidang micro block was subjected to extrusion.