A method for continuous ethylene polymerization under high pressure using a polymerization reaction zone comprises a primary reaction zone and a secondary reaction zone wherein the secondary reaction zone has a length of 1.5-6.5 times the length of the primary reaction zone and a cross-sectional area of 1.2-4 times the cross-sectional area of the primary reaction zone. Ethylene is fed continuously into the primary reaction zone at the starting point of the primary reaction zone. Low temperature initiator alone, or an initiator mixture containing mainly low temperature initiator is introduced into the primary reaction zone at the starting point of the primary reaction zone. Initiator alone or an initiator mixture is introduced into the secondary reaction zone at two or more different points of the secondary reaction zone. Ethylene polymer products of various physical properties are produced with high productivity, while the pressure drop is minimized.