Highly ordered polymer packing is important for organic electronic device because of intra- and interchain charge transport. It is well known that annealing process above glass transition temperature makes polymer be more stable state and have high oredered structure. Many people use thermal annealing process after spin-coating their semiconducting polymer. We found that crystallizable additives such as naphthalene and 1,3,5-trichlorobenzene give highly ordered structure to Poly(9,9-di-n-octylfluorene-alt-benzothiadiazole), which is called ‘F8BT‘. Through Eutectic melting, additives and F8BT can be mixed homogeneously. By cooling mixture, additives are crystallized and it helps F8BT to have ordered structure. Interestingly, when our film with using eutectic melting was annealed at same condition with pristine film, it has more complicated and higher ordered structure. The films were analyzed by grazing incidence wide angle of x-ray Scattering(GIWAXS), AFM, and FT-IR. It was confirmed that GIWAXS of annealed structure with eutectic melting has many diffraction peaks at face-on , which means lamellar supramolecular structure.