该方法包括乙烯的（共）聚合中的180-320℃下在300-2 500巴中的齐格勒型，一个第二分离步骤，第三步骤的催化体系的存在下使第一步骤中所述的方法 未反应的单体和用于再压缩的第四步骤的回收利用，其特征在于，存在被引入到在第一步骤中后期反应介质中，能够降低催化剂体系的金属或过渡金属中的至少一种化合物。 这种化合物可以选自有机锂，有机镁，有机锌，有机镉，有机汞衍生物和一氧化碳。 有利的是，所述化合物的摩尔通量在催化体系的金属或过渡金属的摩尔通量的0.2至6倍之间。 也可以引入，此外，当第二及或第三步骤中，循环单体料流（S）（S）中，并任选地形成（共）聚合物，选自以下的至少一种化合物： - 化合物含有至少两个环氧官能团 - 从4至500个碳原子，含有聚亚烷基多元醇 - 12至22个碳原子，含有饱和或不饱和有机酸酰胺。 这种方法允许在聚合设备的较好的操作，以避免在所形成的（共）聚合物的平均分子量的降低，并防止高分子量聚合物的在再循环回路的形成。

The method which comprises a first step of (co) polymerization of ethylene at 180-320 ° C under 300-2 500 bar in the presence of a catalytic system of Ziegler type, a second separation step, a third step of recycling of unreacted monomers and a fourth step for recompression, is characterized in that there is introduced into the reaction medium late in the first step, at least one compound capable of reducing the metal or transition metal of the catalyst system. Such a compound may be selected from derivatives organolithium, organomagnesium, organozinc, organocadmiens, organomercu- cal, and carbon monoxide. Preferably, the molar flux of said compound is between 0.2 and 6 times the molar flow of the metal or transition metal of the catalyst system. May also be introduced, in addition, when the second andor the third step, in the monomer stream (s) recycled (s), and optionally (co) polymers formed, at least one compound selected from: - Amides of saturated or unsaturated organic acids containing from 12 to 22 carbon atoms, - The polyalkylene polyols containing from 4 to 500 carbon atoms, - Compounds containing at least two epoxide functions. This process allows a better functioning of the polymerization plant, to avoid the decrease in the average molecular weight (co) polymers formed and to prevent the formation of high molecular weight polymers in the recycling circuits.