PURPOSE: To provide a PE compsn. without detriment to characteristics inherent to ultra-high-molecular-weight PE, by mixing high-density PE with ultra- high-molecular-weight PE.

CONSTITUTION: The titled compsn. is obtd. by mixing 65W35wt% high-density PE having a viscosity-average MW of 15,000W8,000 as a fluidity improver with 35W65wt% ultra-high-molecular-weight PE. Since the ultra-high-molecular-weight PE has a very high MW, it is different from usual high-density PE in physical properties and it has a low density and belongs to a medium-to low-density PE. It has well-balanced physical properties such as low friction coefficient, excellent resistance to wear and impact, etc. However, it has disadvantages in that it can not be subjected to extrusion, injection molding, film molding, etc. By mixing high-density PE as a fluidity improver, extrudability can be improved without detriment to excellent characteristics inherent to the ultra-high-molecular-weight PE.