A novel aptamer biosensor for fast tetracyclines determination was established and illustrated in this paper. The tetracyclines aptamer as a specific affinity molecule was immobilized on the surface of the glassy carbon (GC) electrodes. It can specifically bind tetracyclines quickly in milk and other samples without sample treatment. Subsequently, the electrochemical signals are produced and measured accurately. The linear relationship between the currents and the tetracyclines concentration is 0.1-100 ng ml(-1). The sensitivity limit of the device is 1 ng ml(-1). The detection time is 5 min.