Abstract: There is a non-equilibrium ionization zone in the detonation plasma resulted from the non-equilibrium heat release of chemical reaction. Because of the low mass ratio between electron and heavy particle in the non-equilibrium ionization zone, the transfer efficiency between electron and heavy particle is low. And this enhances the non-equilibrium character. The double fluid model of electron and heavy particle is established to explore the non-equilibrium phenomenon in the detonation plasma. The parameters of electron and heavy particles in the non-equilibrium ionization zone of the oxy-hydrogen detonation are calculated by this developed model with the different oxy-hydrogen ratio and initial pressure.