Reducing the required memory bandwidth is a main issue in 3D computer graphics. PN triangle solves the memory bandwidth problem by using curved surface representation and tessellation. It reconstructs a smooth and detailed 3D model from blocky one on graphics hardware and then reduces bandwidth consumption required for data transmission. But the existing PN triangle hardware tessellates a curved surface according to the user-defined and fixed Level Of Detail (LOD) and redundant geometric operations can be executed. In this paper, we insert adaptive LOD concept in PN triangle and propose several schemes for implementation and reducing visual artifacts. Simulation results show the reduced operation count and improved visual quality. Additionally we propose hardware architecture of PN triangle generation unit using adaptive LOD. The required hardware cost for PN triangle generation unit is not overhead to overall 3D graphics hardware.