In order to discover the effect and action mechanism of salt water on performance of organic salt drilling fluid（OSDF)，and to regulate and stabilize the performance of the OSDF, indoor experiments were made to test the influence of salt water intrusion on the performance and stability of OSDF，and the mechanism of salt water intrusion was analyzed. The results showed that the main effect of salt water on the OSDF system was dilution ，which leaded to a decrease in viscosity and shear stress greatly，mud cake thickening and poor settlement stability. when the 40% salt water intrusion，apparent viscosity decreased from 103 mPa·s to 18.5 mPa·s， API and HTHP filitration increased from 1 mL to 2.7 mL and 7 mL to 28.1 mL，respectively；The filter cake thickness of API and HTHP increased from 2 mm and 0.5 mm to 1 mm and 7 mm，respectively；the density difference of the drilling fluid at the temperature of 20℃ and 150℃ increased from 0 g/cm³ and 0.18 g/cm³ to 0.08 g/cm³ and 0.32 g/cm³，respectively. These changes would undoubtedly increase the frequency of underground complex situation.