Hydrophobic long carbon chains (C16) were grafted onto the main chains of Xanthan Gum by etherification under the ordered conformation of Xanthan. Rheology and pyrene fluorescence spectroscopy experiments discovered that the critical association concentration (CAC) of modified Xanthan solution was 0.16%, and ANS fluorescence probe test indicated modified Xanthan had better hydrophobic association effect than before. Additionally, macroscopic and microscopic properties of modified Xanthan solutions, as well as the effects of temperature and salt on its association behavior were explored by rheology and scanning electron microscopy (SEM), revealed the reason of the improvement of modified Xanthan properties in micro levels. The results show that the modified Xanthan had better high-temperature resistance, which retained 421 mPa·s at 140 °C, about four times the apparent viscosity of Xanthan before modification (125 mPa·s). Adding NaCl up to the salt concentration of 4.0%, modified Xanthan still maintained well spatial network structure and a high apparent viscosity (728 mPa·s), while the apparent viscosity of Xanthan before modification was much lower than 728 mPa·s. Since the hydrophobically modification didn’t change the structure of Xanthan, the improvement of the above properties all came from the contribution of hydrophobic chain graft. Graphical Abstract