The ability of fertilizer treatments (O (Optimum level), OP (Optimum level + twice amount of K+), OZ (Optimum level + twice amount of Zn2+) and OZP (Optimum level + twice amount of K+ + twice amount of Zn2+)) to ameliorate salinity stress was studied in canola plants. In addition, fertilizer treatments; O, OZ and OZP couldn’t increase the activity of antioxidant enzymes, such as superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6) and ascorbate peroxidase (APX; EC 1.11.1.11). When these plants were treated with OP treatment, the inhibitory effects of salinity stress were decreased by increasing the membrane stability index and antioxidant enzyme activities by ameliorating the salinity injury. These results suggested that 500 (mg kg-1) potassium has an important role in the enhancement of plant antioxidant systems and resistance to salinity in canola plants.