CdSe nanocrystals wth different morphologies were prepared by using inverse m icroemulsion method and sodium sulfite,selenium powder and chromium nitrate as the raw mater ial.X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques are use d to characterize the structure and morphology of the nanocrystals.The results sh ow that nanocrystals are mainly composed of CdSe(100),CdSe(110),CdSe(112),Na₂SO₄(111),Na₂SO₄(113), Na₂SO₄(220),Na₂SO₄(153),Na₂SO₄(260).The grain size of CdSe (100) d irection is calculated according to the Sherrer formula to be D₁₀₀＝35nm.Short chains-like,necklaces-like and bamboo-like CdSe nanocrystals were prepared under different conditions.The mechanism is as follows:The content of water in interface membrane bound is les s than that of internal free water,which causes the outer density less than the central density of CdSe nanospheres,and the Se2－ and Cd²⁺ are drived to the outer layer to form CdSe hollow nanospheres by concentration difference.Due to kiekendall effect,a lot of holes are formed in t he CdSe nanospheres.center,and holes are fused into larger voids to form CdSe ho llow nanospheres.Because of the small size effect,the CdSe hollow nanospheres become necklace-like nanotubes and ultimate ly bamboo-like nanotubes by oriented attachment mechanism and the surface quali ty diffusion motion.