Abstract: High-density isotropic carbons (HDIC) were prepared from ultra-fine MCMB powders with a particle size of 0.1～0.5μm, much less than that of 5～30μm used in former research. The influence of the nature of MCMB powders and molding conditions on the properties of HDIC were investigated by thermal analysis and SEM. It is found that HDIC sample with a bend strength up to 134.3MPa can be made by molding at 240MPa and carbonization at 1000℃. The excellent self-sintering property of the ultra-fine MCMB is ascribed to a large number of light molecules and some active groups adhering to the surface of MCMB. The hard agglomerates that have a bad effect on the microstructure and bend strength of HDIC originates from the self-sintering property of the ultra-fine MCMB. Grinding is an effective way to destroy hard agglomerates, and as a result improves the mechanical strength of HDIC. Due to the internal friction, tendency to agglomerate, and poor fluidity of ultra-fine MCMB powders, suitable molding pressure and especially holding time are necessary to obtain a homogeneous microstructure in the HDIC, and to alleviate the defects characterized by an inhomogeneous density distribution.