A novel electrochemical sensor was presented for the determination of metronidazole (MDZ), which was based on a graphene (r-GO) modified magnetic-controlled glassy carbon electrode (MCGCE) and magnetic molecularly imprinted polymer (mag-MIP). The mag-MIP was immobilized on the r-GO modified MCGCE (r-GO/MCGCE) or removed from it by freely installing a magnet into MCGCE or not. The as-prepared mag-MIP was used to recognize MDZ from sample solutions to obtain mag-MIP-MDZ. Then, the mag-MIP-MDZ was separated from the solution using an external magnet, rinsed and dispersed in little buffer solution by ultrasound, and part of the suspension was immediately dropped on the r-GO/MCGCE for electrochemical detection. After detection, the magnet was removed from the MCGCE, and the mag-MIP was collected using an external magnet. Afterwards, the magnet was installed into the MCGCE again for the next detection. The used mag-MIP was collected and totally eluted for reuse. The factors concerning the assay strategy were carefully investigated, including preparation conditions of mag-MIP, modified electrode and determination variables. Under the optimal conditions, the electrochemical sensor offered an excellent response to MDZ, the linear detection range was 3.2 x 10(-8) similar to 3.4 x 10(-6) mol L-1 and the detection limit was 1.2 x 10(-9) mol L-1. The method was applied to the determination of MDZ in real samples with satisfactory results. (C) 2014 Elsevier Ltd. All rights reserved.