Irregular shape particles (IRS) are widely existed in engineering, e.g.landsides, debris flow and mud-rock flow.A notable characteristics of these particles include complex geometry of the shape, extremely irregular surface, concave and convex coexist.These features cause particles build-in and interlock between each other, which make the characters of sliding and friction of irregular-shape particles more complex than the regular-shape particles.For revealing the frictional mechanism of the particles, a refined modeling method based on D escrete Element Method (DEM) and CT scanning technique is constructed in which three controlling parameters are introduced to control the accuracy and number of models, moreover, the inertia tensor of IRS particle model are optimized.Furthermore, a calculation method which considering the macro-biting and mesoscopic contact friction of granular materials is proposed by the guidance of molecules-mechanical friction theory.Finally, a numerical open bottom cylinder test is carried out, a functional relationship between the macroscopic and mesoscopic friction parameters of the IRS granular materials is obtained by function fitting method based on numerical test data.The results indicate that the refined modeling method is proved accurate and effective and the function predicting macroscopic internal friction coefficient with relative high precision when the mesoscopic friction coefficient exceeds a specific value (0.3).