In this study the difference of physiological characteristics of four early generations of synthesized Brassica napus allotetraploid(F₁-F₄) and their parents B.napus(AA),B.oleracea(CC) under 100 mmol/L,200 mmol/L NaCl treatments through hydroponics culture was detected.The results demonstrated that the biomass,content of proline,relative chlorophyll,activities of antioxidant enzymes of B.oleracea were the lowest,while the relative conductivity,and MDA content were the highest.Furthermore,the biomass,relative chlorophyll content,activities of SOD of F₂ generation were higher than other materials under 100 mmol/L NaCl treatment,MDA content contrarily.The biomass,relative chlorophyll content,activities of POD of F₄ generation were higher than others under 200 mmol/L NaCl treatment,MDA content contrarily.The results of comparative analysis in the effect of varieties and salt stress suggested that B.oleracea with CC genome is more sensitive to salt stress than B.napus with AA genome.The salt tolerance of four synthesized Brassica early generations is better than diploid parents,because they inherit the salt tolerance performance of B.napus AA genome.