The invention discloses a method for obtaining a dunaliella salina CHYB gene-modified tobacco. According to the method, firstly, tobacco seeds are dipped in the sodium hypochlorite solution and then are cleaned in sterile water. Secondly, the tobacco seeds are dipped in ethyl alcohol, then flushed in sterile water, inoculated in an Murashige and Skoog medium and cultivated to obtain aseptic seedlings. After that, the construction of a plant expression vector Pcambia3301-chyb and the genetic transformation of agrobacterium tumefaciens are conducted. Finally, the transformation of tobacco is conducted based on the leaf-mediated method. According to the method, the dunaliella salina CHYB gene is successfully transferred into tobacco through the agrobacterium tumefaciens-mediated leaf-mediated process. In this way, obtained transgenic tobacco plants are higher in height, leaf area and chlorophyll content compared with plants in a control group. After the stress treatment in 200 mmol / L NaCl, the chyb-modified transgenic tobacco can still survive and grow. Meanwhile, the relative electrical conductivity of tobacco leaves changes slightly, and the proline content in tobacco leaves increases. The salt tolerance of the chyb-modified transgenic tobacco is improved.