幾丁聚醣因為無法溶於純水及中性水溶液而限制了它們的應用；幾丁寡醣或低聚合度幾丁聚醣則由於可溶於水，具有更好之生理活性，因而可廣泛應用於生醫、食品及農業方面。本實驗研究過硫酸鉀(KPS)降解幾丁聚醣之反應機構及反應動力，結果發現在酸性環境下，添加少量的過硫酸鉀即可迅速降解幾丁聚醣分子鏈，同時降解速率隨著過硫酸鉀添加量的增加或溫度的提昇而增加。我們假設了一個以自由基降解幾丁聚醣的反應機構，從此機構中導出一個簡單的反應動力式，進而計算出幾丁聚醣降解速率和KPS濃度的0.40次方成正比。 Applications of chitosan are limited by their insolubility in neutral water and organic solvents. However, chitosan oligomers or low-molecular-weight chitosan can be dissolved in neutral solution and offer better biological activities, such that they are widely used in biomedical applications, food industry and agriculture, etc. In this study, potassium persulfate (KPS) was used to degrade chitosan, further facilitated by an acid environment. Molecular chain of chitosan was found to be degraded rapidly by an addition of a small amount of KPS. The degradation rate was increased with increasing the KPS amount or temperature. A reaction mechanism was proposed based on free radical degradation. According to this mechanism, a simple kinetic model was derived, where the degradation rate was found to be proportional to 0.40 power of KPS concentration.