Poly(diallyldimethylammonium chloride) functionalized helical carbon nanotubes (PDDA-HCNTs) were successfully synthesized. The resulting PDDA-HCNTs composite has good conductivity, solubility and ferromagnetic property. The fabricated HCNTs could be conveniently separated and magnetically attached to the magnetic electrode owing to their excellent magnetic properties. An amperometric biosensor was firstly developed based on glucose oxidase (GOD) functionalized PDDA-HCNTs loaded on magnetic glass carbon electrode. The constructed biosensor exhibited excellent electrocatalytic activity and stability for the detection of glucose with a linear range from 5 to 85μM and a low detection limit of 0.72μM at 3σ. The present work offers a new avenue to broaden the applications of HCNTs in electrochemical biosensors.