OBJECTIVE: To extract collagen protein from scales of fish,to prepare gel and to investigate in vitro diffusion rate of the drug in it.METHODS: The scales of fish were extracted effectively with pepsin and the collagen protein could be prepared after salting out,purification and freeze drying.Collagen protein gel was prepared using a serial mixture of citric acid solution,glycerol and ethanol and with salicylic acid as model drug.The in vitro diffusion rate of collagen protein gel was investigated by agar diffusion method using diffusion coefficient k as index,which was compared with the salicylic acid water-soluble ointment and greasy ointment.RESULTS: The content of collagen protein was 91.04%.The diffusion coefficient k of Salicylic acid collagen protein gel,salicylic acid water-soluble and greasy ointment were 68.11 mm2·h-1,58.04 mm2·h-1,17.67 mm2·h-1.CONCLUSION: Collagen gel can be used for external preparation to make drugs release faster.