In order to evaluate the exact mechanism of an improvement on adhesiveness of poly-ethylene surface by pretreating it with aqueous solution of ammonium peroxydisulfate，stu-dies were conducted by X-ray photoelectron spectroscopy (XPS) and other techniques．From the experimental results，it is shown that oxygen-containing groups such as carbonyl，alde-hyde and carboxyl etc．are produced on the polyethylene surface due tO the oxidative effect of ammoniuln peroxydisulfate．From the results of．XPS analysis．the oxidation depth of high density polyethylene is estimated to be less than 40A，For low density polyethylene，an eyed oxidation layer with a depth between 40 A and 90A is observed．It is shown from the ex-traction experiments，no residue formed by crosslinking is found on the polyethylene sur-face treated by the aqueous solution of ammonium peroxydisulfate．The adhesive strength of the treated polyethylene with epoxy adhesive is apparenray increased．On the basis of the results obtained．the mechanish of the improvement on adhesiveness of polyethylene sur-face by treating it with aqueous solution of ammonium peroxydisulfate was discussed．