A novel heteropolyacid (HPA) and polyethylene oxide (PEO) composite electrolyte was prepared and applied as the solid electrolyte for solid-state dye-sensitized solar cell. Advanced HPA–PEO composite electrolytes could be prepared by the optimized mixture solvent of chloroform and methanol (ChMe), which possessed the enhanced morphological properties, ionic conductivity and amorphicity. It is due to the presence of well-dispersed HPAs on the texture of PEO with the strong interaction between them. DSSCs fabricated with HPA–PEO/ChMe electrolyte showed significantly high photovoltaic (PV) performance with the overall conversion efficiency of 3.1%, open circuit voltage of 0.524V and a short circuit current of 9.7mA/cm2. HPA in the composite electrolytes may act as an electron acceptor to prohibit the photo-reduction of I−, resulting in the advanced photocurrent density and stability without significant decline of the PV performance for 7 days.