Based　on　the　infectious　disease　model　with　disease　latency,　this　paper　proposes　a　new　model　for　the　rumor　spreading　process　in　online　social　network.　In　this　paper　what　we　establish　an　SEIR　rumor　spreading　model　to　describe　the　online　social　network　with　varying　total　number　of　users　and　user　deactivation　rate.　We　calculate　the　exact　equilibrium　points　and　reproduction　number　for　this　model.　Furthermore,　we　perform　the　rumor　spreading　process　in　the　online　social　network　with　increasing　population　size　based　on　the　original　real　world　Facebook　network.　The　simulation　results　indicate　that　the　SEIR　model　of　rumor　spreading　in　online　social　network　with　changing　total　number　of　users　can　accurately　reveal　the　inherent　characteristics　of　rumor　spreading　process　in　online　social　network.