In this work, a novel label-free electrochemical biosensor is developed for the detection of galectin-1 (Gal-1) based on gold nanoparticle (AuNP) loaded octahedral Cu2O (Cu2O@Au) nanocomposites. The AuNPs on the surface of the Cu2O nanocrystals not only enhance the electrochemical performance, but also serve as the binding sites for the lactose ligand which can specifically bind with Gal-1. The Cu2O@Au nanocomposites provide the synergic effect of electrochemical signal amplification and lactose-galectin reaction as the recognition strategy. Under optimal conditions, the proposed biosensor exhibits a variation of electrochemical responses to different concentrations of Gal-1 ranging from 0.1 pg ml-1 to 10 ng ml-1. This work presents an alternative electrochemical biosensor for the detection of tumor biomarkers based on a simple and economical lactose ligand incorporated Cu2O@Au biosensor platform.