(CP2ZrCl2)-Zr-tt (Cp-tt = eta(5)- (Bu2C5H3)-Bu-t) was synthesized by the reaction of LiCptt with ZrCl4 and characterized by X-ray crystallographic studies. It was used as catalyst for ethylene polymerization. Structural analysis was carried out on the polyethylene (PE) catalyzed by (Cp2ZrCl2)-Zr-tt via wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). The degree of crystallinity (W-c,W-x) was calculated by WAXD. The semiaxises of the particles (a, a, b) of PE were determined by SAXS and it could be found that the crystalline particles of PE are mainly rod shaped determined by the characteristic function v(o) (r). The radius of gyration R-g, crystalline thickness L-c, the thickness of noncrystalline region L-a, long period L, electron-density difference between the crystalline and noncrystalline regions eta(c) - eta(a), and the invariant Q are determined by SAXS. The results also indicate that a transition zone exists between the traditional "two phases" with a clear dimension of 1.3 nm. (C) 2005 Wiley Periodicals, Inc.