Strong organic acids, such as phosphoric acid (H₃PO₄), have been trapped in a variety of polymeric solids that have been synthesised from the acid solutions. Polyvinyl alcohol (PVA)-based polymer electrolytes comprising with various concentrations of H₃PO₄ are prepared using a solution casting technique. To study conductivity and charge transport in the solid polymer electrolytes (SPEs), measurements of electrical conductivity and transference number were carried out. The frequency dependent AC conductivity at room temperature obeys the modified universal power law and the DC conductivity was obtained from the fitting parameter. The room temperature protonic conductivities of solid polymer electrolytes PVA-H₃PO₄ is higher than 10^-4 S cm^-1. According to the conductivity results, the ionic conductivity of the samples increases when the amount of acid is increased. The results of the transference number measurements agree with this hypothesis. The films' temperature-dependent conductivity appears to follow the Arrhenius principle. The proton transport mechanisms are affected by acid concentrations. The characteristics of these different solid polymer electrolytes have been examined to increase the protonic conductivity and maybe apply these solid polymer electrolytes in electrochemical devices such as batteries, sensors, and electrochromic devices.