π-Conjugated alternating copolymers containing 2,3-bis(4-octyloxyphenyl)-5,8-bis(seleno-phen-2-yl)quinoxaline as poly(phenylene ethynylene)s (P1), polyfluorenes (P2) and polycarbazoles (P3) were prepared by Sonogashira or Suziki C-C coupling reactions using Pd(PPh₃)₂Cl₂ or Pd(OAc)₂ and tricyclohexylphosphine as catalyst, respectively. The structures of copolymers were performed by FT-IR, ¹H-NMR, ultraviolet and visible spectrophotometry (UV-vis), fluorescence spectroscopy (PL), gel permeation chromatography (GPC), cyclic voltammogram (CV) and XRD, and acidichromic properties of all copolymers were studied in CHCl₃-CF₃COOH mixtures. The results show that all copolymers are soluble in common organic solvents such as toluene, CHCl₃ and tetrahydrofuran (THF), and the maximum absorption at long wavelength appears at 546 nm, 542 nm and 538 nm in CHCl₃solution, and 586 nm, 552 nm, 558 nm in film state. The optical band gap energy of copolymers is 1.80 eV, 186 eV and 1.84 eV, respectively. Comparing with P1 and P2, copolymer P3 displays better acidochromic sensitivity and linear relationship between absorbance and concentration with the concentration of CF₃COOH from 1.346×10^-3 mol/L to 13.46×1010^-3 mol/L. Electrochemical behaviors of polymers depict p-doping and some hole-transporting properties.