Desorption and adsorption isotherms of macadamia nut shell at 25℃ were determined. Non-linear regression analysis was used to evaluate the fitness of the six commonly used models based on the experimental data, and to determine the best models and their parameters. The results showed that the obtained desorption and adsorption isotherms were of type Ⅰ, according to IUPAC’s classification. The hysteresis loop was of type H3. GAB model was the best fitted for desorption and adsorption isotherms. The parameters A, B and C of GAB model for desorption isotherm were 9.693, 0.605 and 8.378 respectively, and those for adsorption isotherm were 9.695, 0.635 and 3.268. The results provided fundamental data for macadamia nut preservation and processing.