Monomer-isomerization copolymerizations of styrene (St) and cis-2-butene (c2B) with TiCl3-(C2H5)3Al catalyst were studied. St and c2B were found to undergo a new type of monomer-isomerization copolymerization, i.e., only isomerization of 2B to 1-butene (1B) took place to give a copolymer consisting of St and 1B units. The apparent copolymerization parameters were determined to be r(st) = 16.0 and r(c2b) = 0.003. The parameters were changed by the addition of NiCl2 (r(St) = 8.4, r(c2b) = 0.05). The copolymers containing the major amount of St units were produced easily through monomer-isomerization copolymerization of St and 2B.