Photoluminescence (PL) and electroluminescence (EL) of mixtures of polyacetylene derivatives with different substituents have been studied in detail. Remarkable spectral shift of PL and EL from blue to green by changing the concentration of poly(diphenylacetylene) (PDPA) derivatives in poly(alkylphenylacetylene) (PAPA) derivatives has been observed. Marked quenching of PL and EL intensities has been found out in disubstituted polyacetylene such as PDPA derivatives upon introduction of monosubstituted polyacetylene. Dependence of PL decay time on molar ratio proportion of mixtures have been also studied. These characteristics have been discussed in terms of fast interchain interaction such as excitation energy transfer between polyacetylene derivatives with different molecular structures.