Abstract: The present invention relates to a process for producing polyethylene of very high molecular weight and a method for activating the catalyst support. The parameters related to the gaseous phase fluidized bed process were determined: the temperature in the reactor, the speed of the cycle gas, the effective time of retention inside the reactor and the concentration values of buten-1 and CO2 in the cycle gas. It also relates to a thermal activation method specially intended for silicate carriers of the chromocen catalyst (the mass loss is coupled with the temperature).