Hi Xuanhong2..... Tinkicka raises some valid points in that any repairs may ultimately fail however from what I can see it is the male portion of the ferrule which has cracked not the female. You have nothing to lose by attempting a repair because to purchase a replacement for the damaged section will likely cost as much as a totally new rod. I am assuming the warranty period has expired. I would simply glue a short length of dowel inside the damaged ferrule using a good quality epoxy. Take care not to force fit the dowel otherwise it will cause the crack to widen and then not allow the male ferrule to fit into the female ferrule after your repair is complete. You could fashion the dowel from cutting up an old no-good fishing rod. Don't make the dowel too long or it won't allow the rod to bend as designed. Good luck with it, the repair could last 10 minutes or ten years.
My 2c......Twosheds