With the use of elemental metals and selenium as resource materials, ZnSe and CdSe nanocrystals have been prepared through an aqueous method at temperature as low as 80 o C in alkaline medium. The products were characterized by powder X-ray diffraction pattern (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectrum (XPS). Two kinds of chemical mechanisms for the formation of the products and the influence of experimental conditions are discussed.