The spectral broadening properties of the amplified spontaneous emission (ASE) generated by a soluble copolymer, Poly[1,8-octanedioxy-2,6-dimrthoxy- 1,4-phenylene-1,2-ethenylene-1,4-phenylene-1,2-ethenylene-3.5-dimethoxy-1,4-phenylene] (CNMBC-Ph), were investigated. The features of the ASE spectra of the CNMBC-Ph solution demonstrated that the broadening of the ASE spectra Is inhomogeneous. The inhomogeneous broadening is supposed to originate mainly from the imperfect configurations of the conjugated polymer with the one-dimensional periodic structure and the spacial inhomogeneous distribution of the chromophores due to disordered distribution of polymers in solution. The influence of inhomogeneous broadening on laser performances was discussed.