Crab chitosan was prepared by alkaline N-deacetylation of crab chitin for 60,90 and 120 minutes and the yields were 30.0-32.2% with that of chitosan C120 being the highest. The degree of N-deacetylation of chitosans (83.3-93.3%) increased but the average molecule weight (483-526kDa) decreased with the prolonged reaction time. Crab chitosans shows lower lightness and WI values than purifies chitin, chotosans CC and CS but higher than crude chitin.