Based　on　the　characteristics　of　rumor　spreading　in　online　social　networks,　this　paper　proposes　a　new　rumor　spreading　model.　This　is　an　improved　SIS　rumor　spreading　model　in　online　social　networks　that　combines　the　transmission　dynamics　and　population　dynamics　with　consideration　of　the　impact　of　both　of　the　changing　number　of　online　social　network　users　and　different　levels　of　user　activity.　We　numerically　simulate　the　rumor　spreading　process.　The　results　of　numerical　simulation　show　that　the　improved　SIS　model　can　successfully　characterize　the　rumor　spreading　behavior　in　online　social　networks.　We　also　give　the　effective　strategies　of　curbing　the　rumor　spreading　in　online　social　networks.