The extraction and purification methods of type Ⅱ collagen from the rat cartilage were established. Kirietics of fibrillogenesis, stability and ultrastructure of fibils of type Ⅱ collagen of cartilage from rats were investigated in vitro in this paper. The results indicated that the tag phase and growth phase were 15 and 120 min respectively, gelatinization rate in growth phase was 0.0060, gelatin reversibility was 13.58%, and collagen fibrils showed typically banding pattern staggered by 64nm, especially for the native fibrils, but the diameters of these fibrils were larger than those in vivo. These data are of importance for studying the formation and regulation mechanism of collagen fibrils in vivo.