Chitosan. a natural biodegradable polymer, was crosslinked with epichlorohydrin in alkaline condition and phosphorylated with P2O5 in methanesulfonic acid to use as a chelating polymer. Insolubility of crosslinking reaction product in acidic solution confirmed that crosslinking was occurred favorably by epichlorohydrin and it was proved that a swelling ratio of crosslinked chitosan(c-chitosan) in acetic acid solution could be thought as a measure of degree of crosslinking. Crofslinking mechanism was presumed from the various crosslinking methods. The effects of crosslinking ratio and phosphorylation conditions(amount of phosphorus-pentoxide, temperature and time) on the phosphorylation of c-chitosan were investigated.