To enhance the hemostatic effect of chitosan, a long chain alkyl group was connected to the amino group of chitosan by acylation to form hydrophobic chitosan. Single factor experiments were used to optimize the temperature and the concentration in the reaction process. The viscosity, degree of substitution and coagulation effect of hydrophobic chitosan were used as evaluation indexes. The optimum conditions were as follows: the temperature 55 ℃, 1% (g / ml) chitosan, 0.3% (g/ml) lauric acid anhydride. Its properties were characterized by IR, NMR and contact angle. It showed that hydrophobic chitosan was synthesized. The results of coagulation experiments showed that the hemostatic effect of hydrophobic chitosan was positively correlated with its degree of substitution in a certain range. When the degree of substitution was less than 9%, the hemostatic effect of 1% (g/ml) hydrophobic chitosan acetic acid solution was not ideal. When the degree of substitution was higher 15%, the same concentration of hydrophobic chitosan acetic acid solution was in a gel state and could not be fully mixed with the blood, and seriously affected the hemostatic effect. It was found that the hydrophobic chitosan with a degree of substitution 9% -15% has a good coagulation effect after mixed with blood and the concentration of hydrophobic chitosan was not less than 0.75% (g/ml). The mouse liver hemostasis experiment showed that hydrophobic chitosan powder could quickly stop bleeding and the effect was significantly better than that of chitosan. Therefore, the hydrophobic chitosan synthesized can significantly improve the hemostatic effect of chitosan. It is expected to be developed into a new quickly hemostatic material in the future.