A type of novel retention and drainage aids, water-soluble carboxymethyl chitin (CCH) with different degree of substitution (DS=0.4, 0.5, 0.6), were prepared using chitin (CH) as the raw material and sodium chloroacetate as etherifying agent. The structure of CCH was characterized by infrared spectroscopy (IR), x-ray diffraction analysis (XRD). The results indicated that carboxymethyl group was successful introduced into CH, which resulted in a destruction of crystalline region of CH. The retention and drainage tests showed that the retention and drainage performances became better with the increasing of DS, and the best performances were obtained when the addition amount of CCH with DS=0.6 was 0.5%. In order to further improve the retention and drainage performances of CCH, CCH/PAC dual system was developed by introducing polymeric aluminum chloride (PAC) with high cationic charge density, the retention and drainage performances of CCH/PAC were significantly better than alone using CCH.