In this paper, a fluid model of electro-optic switch of plasma-electrode Pockels cells (PEPC) driven by one-pulse process is proposed. The model includes a simplified set of fluid continuity equations, Poisson's equation and the electron average energy equation, and these equations are numerically solved with the exponential difference scheme, the classical successive over relaxation method (SOR) and the classical fourth-order Runge-Kutta method, respectively. The evolving characteristics of density of charged particles, electronic temperature, electric field, discharge current, charging voltage of the KDP crystal and the switching efficiency of PEPC are simulated. The model for PEPC, which reveals the relationship between the microcosmic physical processes of gaseous discharge plasma and macrocosmic parameters of PEPC, is very useful for the design of large aperture electro-optic switches.