Enzyme　mimics　now　play　a　significant　role　in　biochemistry.　Especially,　peroxidase　mimics　have　been　widely　used　for　developing　colorimetric　sensors　of　blood　glucose.　The　peroxidase　mimics　previously　reported　could　not　be　recycled　for　reusing　and　may　generate　scattering　to　cause　unwanted　optical　interference　when　it　was　used　for　fabricating　colorimetric　sensors.　We　herein　prepared　a　broad-applicable　and　reusable　magnetic　enzyme-loading　nanoplatform　with　enhanced　peroxidase-like　activity　by　simultaneously　loading　Fe3O4　nanoparticles　(Fe3O4NPs)　and　palladium　nanoparticles　(PdNPs)　on　graphitic　carbon　nitride　(g-C3N4)　nanosheets　(Fe3O4NPs/PdNPs/g-C3N4).　The　prepared　Fe3O4NPs/PdNPs/g-C3N4　possesses　stable　and　enhanced　peroxidase-like　activity　and　good　enzyme-loading　capacity　and　can　be　used　to　load　various　natural　enzymes　to　form　highly-efficient　and　stable　double-active　nanozyme　for　fabricating　colorimetric　sensors　for　the　visual　detection　of　small　molecules.　Especially,　the　magnetic　feature　facilitates　the　magnetic　separation　of　Fe3O4NPs/PdNPs/　g-C3N4　from　sample　solution,　which　is　in　favor　of　recycling　and　eliminating　the　optical　interference　caused　by　nanozyme　in　colorimetric　sensors.　The　prepared　Fe3O4NPs/PdNPs/g-C3N4　has　been　successfully　used　to　load　glucose　oxidase　(GOx)　and　cholesterol　oxidase　(Chox)　to　form　magnetic　peroxidase-GOx　and　peroxidase-Chox　double-active　nanozymes,　which　can　be　used　to　fabricate　colorimetric　methods　for　the　detection　of　glucose　and　cholesterol,　respectively,　with　a　visual　detection　limit　of　15　mu　M　and　a　spectrometry　detection　limit　of　1.0　mu　M.　With　the　developed　glucose　and　cholesterol　detection　methods,　we　have　successfully　detected　glucose　and　cholesterol　in　serum　with　a　recovery　of　98-104%　and　a　RSD　(n　=　5)　＜　5%.　With　high　peroxidase-like　activity,　good　stability,　reusable　features,　and　broad　applicability　of　loading　enzyme,　the　developed　magnetic　Fe3O4NPs/PdNPs/g-C3N4　provided　a　promising　approach　for　fabricating　cost-effective,　sensitive,　and　simple　colorimetric　sensors　for　the　visual　detection　of　various　small　molecules.