The invention belongs to the field of macromolecules and biomedical materials, and relates to a polymer, a block copolymer comprising the polymer as a segment, methods for preparing the polymer and for preparing the block copolymer, a micelle particle or a vesicle particle prepared from the block copolymer, and a composition comprising the polymer, the block copolymer, the micelle particle and/or the vesicle particle. The polymer provided in the invention can be used as a novel biomedical material in in the fields such as pharmaceutical formulations, immunological formulations, and gene delivery reagents.