The　foaming　of　PP　has　encountered　challenges　because　of　its　low　melt　strength　and　semi-crystalline　characteristics.　Introducing　long　chain　branching　(LCB)　onto　the　PP　backbone　and　the　addition　of　particles　as　cell　nucleating　agent　are　the　commonly　used　methods　to　improve　the　cell　structure　of　PP　foams.　In　this　paper,　clay-supported　sodium　benzoate　(NaB-OMMT)　was　prepared　from　Na-montmorillonite　(Na-MMT)　via　the　partial　ion　exchange　reaction　with　surfactant　and　subsequent　reaction　with　benzoic　acid.　The　as　prepared　NaB-OMMTs　were　then　applied　to　prepare　LCBPP/NaB-OMMT　nanocomposites　and　their　foams.　The　dispersion　state　of　clay,　crystallization　behaviors　and　rheological　properties　of　the　nanocomposites,　as　well　as　the　cell　structure　and　compression　properties　of　the　foams　were　investigated.　The　results　show　that　clay　layers　are　mostly　exfoliated　in　the　nanocomposites　with　low　NaB-OMMT　content,　while　intercalated　layers　dominant　with　the　content　reaches　2%　or　higher.　The　melting　temperature　of　the　nanocomposites　decreases　and　the　crystallinity　increases,　while　the　spherulite　size　decreases　compared　to　LCBPP.　The　melt　viscosity　and　elasticity　of　nanocomposites　increase　significantly　when　the　content　of　NaB-OMMT　reaches　2%　or　higher.　LCBPP/　NaB-OMMT　nanocomposites　foams　exhibit　higher　cell　density,　smaller　cell　size　and　its　standard　deviation.　Therein,　the　foam　with　1%　of　NaB-OMMT　shows　the　maximum　cell　density　and　the　minimum　cell　size.　It　is　concluded　that　the　cell　structure　of　the　foam　is　highly　dependent　on　the　content,　dispersion　state　and　structure　of　the　cell　nucleating　agent.　When　NaB　is　supported　on　well　dispersed　and　exfoliated　clay　layers,　the　cell　nucleation　efficiency　is　significantly　enhanced.　The　compression　properties　of　the　foams　depend　on　their　cell　structures　and　exhibit　the　similar　variation　trend　with　the　latter　with　the　content　of　NaB-OMMT　increasing.