Collagens were extracted from the grass carp skin and scale by the acid-enzyme combination method. Their structural properties were analyzed by ultraviolet spectrum (UV), sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). And the self-assembly behavior of collagens were compared by turbidity experiment, detection of fibril formation and scanning electronic microscopy (SEM).The results indicated that collagens from grass carp skin and scale were characterized as type I collagen , containing two α-chains,  and maintained a triple helix structure. Denaturation temperatures of the collagens from scale and skin were 34.99 °C and 39.75 °C, respectively. The self-assembly curves showed that the collagens could self-assemble into fibrils at 30 °C near neutral pH with NaCl, and the self-assembly degree of collagens were similar (skin 28%, scale 27.33%). Scanning electronic microscopyobservations suggested that both of the collagens could form intertwine fibril network. The reticular fibrous structure of the scale collagen was more obvious than skin collagen, and a periodic striped D-band was observed. While the skin collagen fiber structure has a collapse and no D-band.