Sodium lauryl sulphate interacts with amino groups in chitosan to form aliphatic groups.Based on the hydrophobic index and contact angle results, SDS-modified chitosan render hydrophobic property than chitosan. Adsorption capacity of synthetic cutting fluid on SDS-modified chitosan is greater than that on chitosan. Therefore, not only surface area and size of pore diameter of adsorbent but also hydrophobic interaction between adsorbent and adsorbate should be considered as an important factor in adsorption.