Conjugated PPV-derived block copolymers containing 2-ethylhexyloxynaphthalene unit were synthesized and characterized in this study. The resulting polymers were soluble in common organic solvents and showed good thermal stabilities, The weight-average molecular weights ($M_w$) of the copolymers ranged from 246,000 to 475,000 with PDIs of $1.3{sim}2.1$. The optical properties of these polymers, measured both in a chloroform solution and on a film, showed a maximum absorption at $405{sim}476;nm$ for Copolymers $I{sim}VIII$. In the PL spectra, Copolymers $I{sim}VIII$ showed maximum peaks at $510{sim}566;nm$. The HOMOs, LUMOs and band gaps of the PPV derivatives of Copolymers $I{sim}VIII$ were $5.30{sim}5.77$, $3.04{sim}3.24$, and $2.5{sim}2.2;eV$, respectively, The multi-layered, light-emitting diodes of ITO/PEDOT/copolymers/LiF/Al exhibited turn-on voltages of $6{sim}2.5;V$ Copolymer VIII exhibited the maximum brightness of $3.657;cd/m^2$. Particularly, Copolymer VII, with an identical composition of MEH-PPV and naphthalene-PPV, showed a maximum luminance efficiency and power efficiency of 2,63 cd/A and 1.06 lm/W, respectively.