In this article， the collagen is extracted from swim bladder of grass carp (Ctenopharyngodon idella) by enzymolysis and its self-assembly is conducted. Composite film was made from self-assembled collagen， chitosan and glycerinum， and its properties were analyzed. Moreover， the effects of coating film on squid quality during cold storage were investigated. The results showed that collagen extracted from grass carp swim bladder belong to type I collagen and had a triple helix structure. The tensile strength of the film made from self-assembled collagen increases， and its elongation at break and water vapor transmission decrease. In addition， the spoilage of untreated squid was occurred on the eighth day， at the time the quality of squid treated with film made from self-assembled collagen was kept well. The values of TVB-N， microbial counts， K value and trimethylamine of squid treated after self-assembled collagen stored for 14 d at 4 ℃ were 21.53 mg/100 g， 5.67 lg(CFU/g)， 14.33% and 25.87 μg/g， respectively， which meant that coating film made from self-assembled collagen could slow down the corruption of squid and prolong the shelf life.