In order to enrich and improve the geohazard-pregnant mechanism of structural mélange, taking the North Lancang River suture zone as an example, the structural petrology characteristics of the structural mélange were dissected, then the physical and mechanical characteristics were identified through field geological investigation and laboratory test analysis, and finally its geohazard effect were revealed. The results show that the tectonic mélange in the northern Lancang River suture zone is sandwiched between granite and granite gneiss on the southwest and volcano-sedimentary rocks on the northeast as a non-abutment layer. The main rock types are phyllite and slate with a small amount of basalt, limestone and siliceous rock blocks, showing obvious “hybrid accumulation” characteristics. Under the coupling process of tectonic uplift, differential weathering and river erosion, it gradually evolved into a mountain deep canyon landform, which is the topographic basis for the development of geohazard. In terms of structural petrology, the structural mélange in the North Lancang River suture zone shows the characteristics of “one weak and three strong”, that is, weak metamorphism, strong deformation, strong alteration and strong orientation, which leads to serious deterioration of rocks and is the source basis of geohazard. In terms of physical and mechanical properties, the tectonic mélange appears as a set of easy to slip soft rock “formation”, rich in clay minerals, with high porosity and water absorption, low compressive and shear strength, which provides structural conditions for the development of geohazards. Tectonic activity and tectonic stress are strong in the North Lancang River suture zone, which provides dynamic conditions for the development of geohazards. The research results are conducive to further enriching and improving the geohazard breeding mechanism of tectonic mélange.