Abstract: In this study, wild type(WT) and transgenic Arabidopsis thaliana carrying SlMIP gene were used to evaluate the change characteristics of osmotic adjustment under different levels of NaCl stress. The results show that the transgenic Arabidopsis carrying SlMIP gene significantly decreases the damage of cell membrane and tissue osmotic potential compared to the wild type, and the transgenic Arabidopsis could maintain higher water content and better growth performance under the salt stress. The content of Na+ and ratio of Na+/K+ in the transgenic Arabidopsis are obviously lower than those in the wild type, while the content of K+ in the transgenic Arabidopsis is higher than that in the wild type plants. In addition, the transgenic Arabidopsis has more accumulation of proline and soluble sugar compared to the wild type Arabidopsis, indicating that the transgenic Arabidopsis thaliana could enhance the organic solute adjustment ability by increasing the uptake of water molecular and decreasing the entrance of Na+ which lead to increase in the content of proline and soluble sugar. Data seems to imply that the transgenic Arabidopsis can more effectively regulate the inorganic exchange by ion compartmentation and interaction with Na+/H+ antiporter, which is located in plasma membrane. These suggest that the transgenic Arabidopsis shows stronger salt tolerance compared to the wild type, and Solanum lycopersicum MIP aquaporin plays an important role in plant osmotic adjustment under the slat stress.