Abstract: Degradation of chitosan by high voltage pulsed discharge plasma (HVPDP) was investigated.The Influence factors were chitosan concentration, acetic acid concentration, the distance between the electrodes and treatment time.The structure of the degraded chitosan was characterized by FT-IR, X-ray.Results showed that treatment time were positive.Chitosan concentration, acetic acid concentration and the distance between the electrodes were negative.The average molecular weight was 298.87ku, the degradation rate increased up to 73.74 % after chitosan concentration 0.3 %, acetic acid concentration 0.5 %, the distance between the electrodes 2mm, treatment time 180min.The main polysaccharide structure of the degraded chitosan still remained.However, the partial amino groups of chitosan were eliminated during the plasma degradation process.The crystalline structure of the degraded chitosan were destroyed.