The synthesis of a star polymer with poly(phenylacetylene) arms was examined. 1,4-Diethynylbenzene, which has a similar structure to the monomer, was added as linking agent to the living polymerization system of phenylacetylene by [(nbd)RhCl](2)/Ph2C=C(Ph)Li/Ph3P ternary catalyst. A star polymer was selectively formed, and the linear polymer was virtually completely consumed. The M-n and arm number of a typical star polymer were 145 000 and 25, respectively. Since the arm number of the star polymer increased with increasing concentration of the linking agent and temperature of the linking reaction and with decreasing DPn of the linear polymer, the arm number could be controlled by these factors. Further, star block copolymers composed of blocks of phenylacetylene and (4-methylphenyl)acetylene were prepared.