Abstract: Mesophase pitch-based carbon fibers have a higher modulus and thermal conductivity than other carbon fibers. A good spinnable mesophase pitch is key to prepare high performance carbon fibers. In this paper, the preparation and characterization of mesophase pitches are reviewed. Spinnable mesophase pitches have been prepared from petroleum pitch or coal tar pitch by heat and catalytic polycondensation. Sometimes, hydrogenation, catalytic polymerization and co-carbonization were used to modify the chemical structure of the pitch before polycondensation. Traditional characterization of mesophase pitch include the softening point, rheology properties, optical anisotropy, average molecule weight and chemical structure. With the rapid progress of characterization techniques, other characterization of the microstructure is possible, such as high resolution MALDI ToF MS which gives the elemental formula of thousands of molecular constituents, which helps improve our understanding of the molecular structure of spinnable mesophase pitches.