pi-Conjugated organoboron polymers were prepared by haloboration-phenylboration polymerization between diyne monomers and bromodiphenylborane. The polymerization was carried out by adding a slightly excess amount of bromodiphenylborane to a tetrachloroethane solution of diynes at room temperature under nitrogen and stirring the reaction mixture for 4 hours at 100 degrees C. The obtained polymers were soluble in common organic solvents such as THF and chloroform. Their molecular weights were estimated to be several thousands by gel permeation chromatographic analysis. In UV-vis absorption spectra, bathochromic shift of lambda(max) and absorption edge in comparison with the corresponding monomers were observed, which indicates the pi-conjugarion via vacant p-orbital of boron atom.