Distribution of active centers(ACD)of ethylene or 1-hexene homopolymerization and ethylene-1-hexene copolymerization with a MgCl2/TiCl4 type Z-N catalyst were studied by deconvolution of the polymer molecular weight distribution into multiple Flory components.Each Flory component is thought to be formed by a certain type of active center.ACD of ethylene-1-hexene copolymer with very low 1-hexene incorporation was compared with that of ethylene homopolymer to see the effect of introducing a-olefin on ethylene polymerization.On the other hand.ACD of ethylene-1-hexene copolymer with very low ethylene incorporation was compared with that of 1-hexene homopolymer.Adding small amount of 1-hexene in ethylene polymerization caused marked activation of all the Flory components of the polymer.in which the low molecular weight components are activated more than the high molecular weight components.In 1-hexene polymerization system,the activity can also be greatly enhanced by introducing small amount of ethylene.but the different Flory components(or active centers) are activated with similar extent,except a newly emerged active center producing polymer with the lowest molecular weight.The total number of active centers is markedly increased by adding small amount of ethylene in 1-hexene polymerization,but the average catalysis efficiency of the active centers decreased.The broad composition distribution of the ethylene-1-hexene copolymer Can be well understood from the ACD of catalyst and is dependence on the monomer.