A　new　signal　amplification　strategy　based　on　back-conjugation　of　biofunctionalized　magnetic　beads　holds　promise　to　improve　the　sensitivity/detection　limit　of　quartz　crystal　microbalance　(QCM)　immunosensor　toward　target　carcinoembryonic　antigen　(CEA,　a　kind　of　tumor　marker)　with　the　help　of　an　external　magnetic　field.　To　construct　such　an　affinity　reactor,　anti-CEA　capture　antibody　was　initially　immobilized　onto　a　10 MHz　quartz　crystal　resonator　by　using　mercaptopropionic　acid,　whilst　detection　antibody　was　covalently　conjugated　to　carboxylated　magnetic　beads　via　a　typical　carbodiimide　coupling.　Sandwich-type　protocol　was　successfully　introduced　to　develop　a　new　high-efficiency　QCM　immunosensor　through　interaction　of　the　carried　magnetic　beads　with　external　magnetic　field.　Under　the　optimal　conditions,　the　linear　range　and　limit　of　detection　(LOD)　of　the　QCM　immunosensor　were　1.0–15 ng mL−1　and　0.86 ng mL−1　CEA　without　external　magnetic　field,　and　0.05–10 ng mL−1　and　0.013 ng mL−1　CEA　in　the　presence　of　magnetic　field,　respectively.　In　addition,　our　system　also　exhibited　good　precision　and　reproducibility,　high　selectivity,　acceptable　stability　(90.3%　of　the　initial　signal　after　a　storage　period　of　24　days),　and　could　be　utilized　for　detection　of　real　human　serum　samples　with　consistent　results　comparable　to　those　obtained　from　commercially　available　enzyme-linked　immunosorbent　assay　(ELISA)　method.　©　2016　Elsevier　B.V.