PURPOSE: To obtain an ethylene polymer which can have a regulated melt rheology activation energy and have regulated physical properties including density, melting point, and crystallinily without incorporation of any ingredient, and which has excellent processability, a high melting point, and excellent impact resistance by polymerizing ethylene using a specific polymerization catalyst under a specific polymerization condition.

CONSTITUTION: Ethylene is polymerized using a polymerization catalyst comprising a suitable combination of a transition metal compound (A) and a compound capable of forming an ionic complex with either the compound (A) or a derivative thereof. The polymer obtained has terminal unsaturated groups and contains no quaternary carbon in the main chain. The polymer has a density of 0.85-0.95g/cm3, a weight-average mol.wt. in terms of polyethylene of 5,000-2,000,000, the ratio of weight-average mol.wt. to number-average mol.wt. (Mw/Mn) in terms of polyethylene of 1.5-70, a melt rheology activation energy of 8-20kcal/mol, and a β dispersion peak at 0 to -100°C in its loss modulus curve.