In this paper, a novel sensing platform for nitrite based on magnetic Co@carbon nanocages (CoCN) was firstly proposed. The metal organic framework (MOF) of ZIF-67 was calcined in argon atmosphere to prepare magnetic CoCN. The synthesized CoCN was fixed on the surface of magnetic glassy carbon electrode (CoCN/MGCE) to fabricate the sensing platform by its magnetism. This sensing platform has advantages of binder-free and easy preparation. The prepared CoCN/MGCE displayed excellent performance for electrocatalytic oxidation of nitrite. Under the best conditions, the peak current of nitrite on oxidation is linear to its concentration from 5 to 705 mu M, with a 0.18 mu M detection limit. The proposed sensor was applied for detecting nitrite in the real sample with 97.0-103.5% recovery range and under 3.6% RSD. The experimental results show that the magnetic CoCN is a novel material for fabricating electrochemical sensing platform.