Poly[(methylsilylene ethynylene phenylene ethynylene)-co-(tetramethyldisiloxane ethynylene phenylene ethynylene)] was synthesized by polycondensation reaction of m-diethynylbenzene magnesium reagent with 1,3-dichlorotetramethyldisiloxane and dichloromethylsilane. The copolymer was characterized by FT-IR, 1 H NMR, differential scanning calorimetry and thermogravimetric analysis. The results show that the copolymer exhibits good processability and cures at low temperatures. The cured copolymer shows high thermal stability.