Using tomato variety ‘Qin Feng Bao Guan’ as experimental material and by the method of hydroponics nutrient solution,we studied the effects of single and compound application of salicylic acid (SA) and sodium nitropprusside (SNP an exogenous nitric oxide donor) on tomato seedling growth and physiological characteristics under the 100 mmol·L^-1 NaCl stress.The results showed as follows:single and compound application of SA or SNP could significantly promote activities of seedling leaf protective enzymes (SOD,POD,CAT),enhance the content of chlorophyll and proline and the vitality of seedling roots and decrease leaves electrolyte leakage and the content of malondialdehyde (MDA),which could alleviate the damage to seedling caused by salt stress and promote the growth and development of seedling and the compound application of SA and SNP which is the best has a certain synergy to improve the salt tolerance of tomato seedlings.