A　new　type　of　mixed　lanthanides-immobilized　(Tb3+,　Tm3+,　Ho3+,　Lu3+)　magnetic　nanoparticles,　Fe3O4@　TCPP-DOTA-M3+,　was　prepared　with　a　particle　size　of　approximately　30　nm.　A　model　protein,　alpha-casein,　and　a　protein　mixture　of　alpha-casein　and　BSA　(1:100)　were　first　used　to　test　the　phosphopeptide　enrichment　efficiency　of　the　newly　developed　magnetic　nanoparticles.　For　the　model　protein　alpha-casein,　19　phosphopeptides　were　identified　with　the　newly　developed　materials.　Even　in　the　tryptic　digest　of　alpha-casein　and　BSA　(1:100),　16　phosphopeptides　were　easily　detected,　suggesting　that　the　novel　materials　possess　high　selectivity　in　phosphopeptide　enrichment.　To　evaluate　the　phosphopeptide　enrichment　efficiency　in　a　real　biological　sample,　the　materials　were　used　to　capture　phosphopeptides　in　the　tryptic　digests　of　an　extract　of　HeLa　cells.　In　total,　9048　phosphopeptides　corresponding　to　2103　phosphoproteins　were　identified　in　a　single　mass　spectrometric　analysis,　indicating　the　great　potential　of　the　new　materials　for　practical　applications.　Compared　with　metal　oxide-based　enrichment　methods,　the　newly　developed　materials　are　convenient　to　prepare　and　easy　to　handle,　and　they　save　time　in　the　phosphopeptide　enrichment　procedure,　making　these　materials　a　good　choice　for　highly　selective　and　sensitive　phosphopeptide　enrichment　in　future　phosphoproteome　analyses.