A monosubstituted ionic polyacetylene having a quaternary ammonium salt was synthesized and characterized. The polymerization of dimethylphenylpropargylammonium bromide (DMPPAB) was performed by various transition metal catalysts to give the resulting polymer in high yield. The polymer structure was characterized by various instrumental methods to have a conjugated polymer backbone system having the designed substituent. This polymer was mostly soluble in organic solvents. The electrochemical properties of poly(DMPPAB) were measured and discussed.