Abstarct: Tomato plants are sensitive to cold with a vast, global culture. Ethylene hormone interferes with non-living stresses such as cold stress. Therefore, aimed at better understanding of the mechanisms of cold responses in tomato, the activity of antioxidant enzymes and the exxpression of some genes that are involve in the biosynthesis of ethylene was investigated in the two different species including S.habrochaites (resistant to cold) and S.lycopersicum (sensitive To cold). The results showed that under temperature stress of 4 ° C, SAM1, SAM2, SAM3, SAM4, SAM5, ACS1 and ACO1 genes had increased exxpression in sensitive species, whereas under cold stress in resistant species SAM1, SAM3 , SAM4 and ACS1 increased exxpression and SAM2 and ACO1 genes reduced exxpression, and there was no significant change in exxpression of SAM5 gene. The difference in the exxpression of ACO1 gene under cold stress in two resistant and sensitive species indicates that ethylene might negetively regulates cold tolerance in tomatoes. Also, the activity of antioxidant enzymes such as catalase and guaiacol peroxidase decreased under stress conditions in both tomato species. The increase in electrolyte leakage and malondialdehyde was also lower in resistant species in comparison to sensitive species at 4 °C. The results of this study are the first report of the role of SAM genes in cold stress, which can be used to identify cellular signaling paths and to create resistant lines.