Objective:　To　study　the　cellular　compatibility　of　the　magnetic　nanocomposite　(n-HA/PLLA/Fe2O3)　and　to　discuss　the　biological　behaviors　of　cells　including　surface　adhesion,　proliferation,　and　expression.　The　present　work　provides　an　experimental　basis　for　medical　application.　Method:　Rat　osteoblasts　(OB)　were　co-cultured　with　the　magnetic　nanocomposite.　Cell　proliferation,　cell　adhesion,　and　the　expression　of　type　I　collagen　(Col-I)　and　osteocalcin　(OCN)　gene　were　characterized　by　the　cell　counting　kit-8　(CCK-8)　method,　scanning　electronic　microscopy　(SEM),　and　reverse　transcription　polymerase　chain　reaction　(RT-PCR),　respectively.　Results:　CCK-8　detection　showed　that　there　was　no　difference　in　cell　proliferation　on　the　magnetic　nanocomposite　between　the　experimental　group　and　control　group　(P　＞　0.05).　SEM　indicated　that　a　large　amount　of　cells　adhered　to　the　surface　and　in　the　pores　of　the　magnetic　nanocomposite.　As　the　co-culture　time　increased,　the　cells　adhering　to　the　magnetic　nanocomposite　showed　an　obvious　increase.　RT-PCR　detection　showed　that　as　the　co-culture　time　increased,　the　expression　of　the　Col-I　gene　was　enhanced　(P　0.05).　There　was　no　obvious　difference　in　the　expression　of　the　OCN　gene　(P　＞　0.05).　Conclusion:　The　magnetic　nanocomposite　is　suitable　for　cell　adhesion,　growth,　and　differentiation　with　a　high　cellular　compatibility.