Abstract: In order to increase degradability and mechanical property of starch-based plastics films, it is necessary that starch is modified by hydrophobic and lipophilic treatment. With cross-linked starch (CST) as a raw material and the organic silane coupling agents KH570 as a modifier, dry method was used to improve the hydrophobic and lipophilic property of cross-linked starch. By using four-factor quadratics rotary orthogonal combination experiment design method and response surface analysis, a regression model of hydrophobic modified starch was obtained. The hydrophobic modified starch was characterized by rotational viscometer, biomicroscopy and infrared spectrometer. The results indicate that the optimized processing parameters of hydrophobic modification are alcohol concentration 95.70%, amount of KH570 1.68% (dry starch base), dilution degree 2.81%, and reaction time 29.61 min. The minimum capacity of water adsorption of hydrophobic coupling cross-linked starch(KCST) is 16.23%, the adsorption rate decreases by 42.44% and 33.2% compared with nature starch and cross-linked starch (CST). With the deepening of hydrophobic modification，the dispensability of modified starch in organic solvent liquid paraffin is markedly enhanced. The particle shape changes from rarefaction to cluster grape ball agglomeration state. The long chain group of methoxyl silane coupling agents KH570 is linked with the anhydrous glucose units of the cross-linked starch.