In order to determine effects of the magnetic tracer for soil erosion on Chinese cabbage, a field experiment was carried out, with the cabbage exposed to the tracers different in concentration (1%, 3%, 5% and 10%). Results show that in all the four treatments, leaf length, leaf width, root length and yield of the plant were all increased significantly. In Treatments 3% and 5%, the tracer improved plant height, chlorophyll content (p<0.05), net photosynthetic rate and transpiration rate as well. The tracer inhibited SOD (Superoxide dismutase) activity in leaves of the plant, but stimulated the activity in roots significantly (p<0.05), however, its effect on POD (peroxidase) in the plant was just the opposite and its effect on CAT (catalase) activity little. In plants exposed to low concentrations of the tracers, POD activity and CAT activity both remained high in leaves and roots. The tracer also caused increase in MDA (malondialdehyde) content significantly (p<0.05) in seedling leaves, but decrease in content of soluble sugar, though not significant. When higher than 5%, the tracer significantly decreased vitamin C in the plant (p<0.05), but when lower than 3%, it improved quality of the plant effectively. In a word, the tracer low in concentration promotes growth of Chinese cabbage, but when high in concentration, it displays an opposite effect on the plant.