With DNA walking machine and cascading catalysis for signal amplification, the electrochemical biosensor achieved excellent sensitivity for detection of BCR/ABL fusion gene with the linear range from 0.2 fM to 20 nM and limit of detection down to 0.05 fM, which could provide a powerful bioanalysis tool for clinical diagnose of CML. Here, BCR is linked to chronic myelogenous leukemia, BCR-ABL1 positive.