The whole deformation process of polyethylene spherulites from spherulitic to fi-brillar structure during uniaxial drawing was investigated under electron microscope. From electron microscopy and wide and small angle electron diffraction pattern it i8 demonstrated that the folded chain blocks aligned perpendicular to the draw direction are further incorporated into micro-fibrils highly aligned in the draw direction. These micro-fibrils are the basic structural elements of polyethylene fibre.