Kimchi is a fermented Korean vegetable product prepared using mafor raw materials (oriental cabbage and radish) and other ingredients through a series of processes of grading, brining, blending, and fermentation. Kimchi fermentation is initiated by various microorganisms originally present in the raw materials, but the fermentation is gradually dominated by lactic acid bacteria. Thus, the complex biochemical activities obviously occur during, before and after kimchi fermentation and their biochemical characteristics greatly differ, depending on the raw materials and processes used. This review covers in detail the numerous biochemical characteristics of sugars, organic acids, amino acids, vitamins(B complex, carotene and ascorbic acid), pectic substances, flavor components and others during preparation and preservation of kimchi.