The　oscillation　of　diffraction　efficiency　is　observed　in　the　nonvolatile　holographic　recording　of　lithium　niobate　crystals　doped　with　iron　and　copper.　The　physics　of　oscillation　in　doubly　doped　lithium　niobate　crystals　is　studied　by　using　Runge-Kutta　methods,　and　the　oscillation　can　be　attributed　to　the　redistribution　of　electrons　in　the　deeper　and　shallower　traps　of　the　crystals　in　the　initial　phase　of　holographic　recording.　The　effects　of　Fe　concentration　and　intensity　ratio　of　red　beams　to　UV　beam　(I-R/I-UV)　on　the　oscillation　are　investigated　theoretically.　The　results　show　that　with　lower　Fe　concentration,　the　amplitude　of　oscillation　is　larger　and　with　lower　intensity　ratio　I-R/I-UV,　the　duration　of　the　oscillation　is　longer.　(C)　2013　Elsevier　GmbH.　All　rights　reserved.