Chitosan oligosacharide is a product of deacetylation of chitosan, which plays an important role in regulating plant growth and development. In recent years, chitooligosaccharides as elicitors can induce plant resistance, which has been widely concerned by researchers. The effects of Chitooligosaccharides on plant stress resistance have been reported, but there are no reports on the induced resistance of sugarcane to chitooligosaccharides. In this experiment, ROC22 was used as experimental material, and chitosan oligosaccharide solution with concentration (w / V) of 25 mg / L, 50 mg / L and 75 mg / l was sprayed at room temperature. The effects of chitooligosaccharide (COS) treatment on polyphenol content and activities of several related resistant enzymes in sugarcane leaves were studied. Chitinase, an important disease protein, was determined by 3,5-Dinitrosalicylic acid (DNS) method, and the reaction conditions were optimized. In addition, the changes of protein content in sugarcane leaves after chitosan oligosaccharide treatment were studied. The results showed that: 1. The content of polyphenols in sugarcane leaves increased with different concentration of chitosan oligosaccharide solution, and the higher the treatment concentration, the more obvious the increase of polyphenol content. Among them, 75 mg / L treatment had the best effect. On the first day, the polyphenol content was 1.8 times of the control. 2. The activities of polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL) and peroxidase (POD) in sugarcane leaves were increased by chitosan oligosaccharides at three concentrations. After treatment with different concentrations of chitooligosaccharides, the activities of the three enzymes increased differently. 75 mg / L chitooligosaccharide solution was beneficial to the induction of POD activity, which reached the peak on the third day, which was 2.5 times of the control. 50 mg / L chitooligosaccharide solution was beneficial to the induction of PAL activity and PPO activity. PAL activity was 1.8 times higher than that of control on the second day, and PPO activity was 1.8 times higher on the first day. 3. The optimum conditions for the determination of chitinase activity by 3,5-Dinitrosalicylic acid (DNS) method were as follows: the dosage of 3,5-Dinitrosalicylic acid was 9.45 mg · g-1, the color developing time was 10 min; the optimum reaction time was 1 h, the optimum temperature was 60 ℃, and the optimum pH value was 7.0. The results showed that chitinase activity in sugarcane leaves could be improved by chitosan oligosaccharide solution of three concentrations, and the effect of 50 mg / L chitooligosaccharide solution was the most obvious. 4. The protein content of sugarcane leaves changed with time after treatment with three different concentrations of chitooligosaccharides. The changes of protein content were different in different concentrations. The treatment of 50 mg / l had a great effect on the protein content of sugarcane leaves.