Abstract:The tomato (Lycopersicon esculentum Mill. ) seedlings were treated in magnetic field and with magnetized water at cotyledon stage and euphylla stage and exposed under different lower temperature condition of certain duration. The results showed that the SOD isoenzyme activity ratio of A-band (Mn-SOD), being more sensitive to lower temperature, to the summation of A-band, B-band (Cu-Zn-SOD)and C-band (Cu-Zn-SOD) was higher than controls. As a result of magnetic treatments the decrease extend of SOD specific activity and the increase extend of conductivity, induced by lower temperature stress, were less than controls. The chilling injury symptoms of treated seedlings were alleviated. The experimental results illustrated that the magnetic treatments brought out certain benefits in raising chilling resistance of tomato seedlings.