The　development　of　low-cost　adsorbent　is　an　urgent　need　in　the　field　of　wastewater　treatment.　In　this　study,　sludge-based　magnetic　biochar　(SMB)　was　prepared　by　pyrolysis　of　sewage　sludge　and　backwashing　iron　mud　without　any　chemical　agents.　The　samples　were　characterized　by　TGA,　XRD,　ICP,　Organic　element　analysis,　SEM,　TEM,　VSM　and　BET.　Characterization　analysis　indicated　that　the　magnetic　substance　in　SMB　was　Fe3O4,　and　the　saturation　magnetization　was　25.60　emu　&　BULL;g(-1),　after　the　adsorption　experiment,　SMB　could　be　separated　from　the　solution　by　a　magnet.　The　batch　adsorption　experiment　of　methylene　blue　(MB)　adsorption　showed　that　the　adsorption　capacities　of　SMB　at　298　K,　308　K　and　318　K　were　47.44　mg　&　BULL;L-1,　39.35　mg　&　BULL;L-1,　and　25.85　mg　&　BULL;L-1,　respectively.　After　one　regeneration　with　hydrochloric　acid,　the　maximum　adsorption　capacity　of　the　product　reached　296.52　mg　&　BULL;g(-1).　Besides,　the　adsorption　kinetic　described　well　by　the　pseudo-second　order　model　revealed　that　the　intraparticle　diffusion　was　not　just　the　only　rate　controlling　step　in　adsorption　process.　This　study　gives　a　reasonable　reference　for　the　treatment　of　sewage　sludge　and　backwashing　iron　mud.　The　product　could　be　used　as　a　low-cost　adsorbent　for　MB　removal.