This paper proposed a physical model of electron trapping/detrapping in electrically stressed oxide. The new model is based on both inelastic multi-phonon trap-assisted tunneling and thermal emission, and the capture effect of oxide bulk traps is considered as well. The dynamic procedure of traps capture and emission of electrons are established. Finally, the filling state of all the oxide traps at any stress and any time can be obtained accurately and effectively which is very useful for the modeling of the endurance and data retention characteristics of floating gate nonvolatile memories.