This paper mainly experimentally studies the imidacloprid degradation in an atmospheric dielectric barrier discharge (DBD) plasma. The effects of DBD discharge parameters, temperature and initial concentration on the degradation ratio were investigated with the help of high-performance liquid chromatography (HPLC). The analyses of HPLC-MS (mass spectrometry) and the comparison with database proved that after plasma treatment four new degradation products were generated. It shows that plasma treatment can effectively degrade imidacloprid and the degradation effect depends on the initial concentration of imidacloprid as well as discharge voltage and treatment time. Under the proper plasma parameters, the degradation ratio can be up to 98%. The increase in temperature caused by plasma discharge only affected the degradation ratio by a few percent, which is negligible compared to that by plasma itself. These results show that low temperature plasma has the potential to be an effective imidacloprid degradation method.