Silicon is the second most abundant element in  soil. It is generally considered a beneficial element for the growth of higher plants, especially those grown under stressed environments. Cadmium is a toxic and nonessential element for plant growth and development. The aim of this study was to investigate the effect of silicon on cadmium stress improvement in tomato. Therefore, the interactional effects of cadmium (0, 50, 100 µM) and silicon (0, 50, 100 mM) were studied. A completely randomized design study with three replications was conducted in the research laboratory of Shiraz University in 1392. The results showed that cadmium exposure significantly decreased plant growth, the content of chlorophyll and carotenoid pigments. Further, increasing 9 times proline, %19.3 anthocyanins and %33.3 the potential total antioxidant, were as consequences of cadmium stress. Lipid peroxidation in roots and shoots increased during stress. The application of silicon significantly alleviated the adverse effect of cadmium toxicity in tomato seedlings. This was correlated with reduction of lipid peroxidation in root and shoot and stimulation of antioxidative activity. Silicon significantly improved growth and photosynthetic pigments in plants under cadmium stress. In all examined parameters, the treatment 100 mM of silicon had maximum effect of improving potential .Therefore, the concentration of 100 mM silicon is proposed as alleviation of cadmium stress such as oxidative stress in tomato.