System and relative process for the complete and high-productivity hydroconversion of heavy oils essentially consisting of a solid accumulation reactor and a stripping section of the conversion products outside or inside the reactor itself.In particular, the system proposed consists of a solid accumulation hydroconversion reactor in which the solids deriving from and generated by the feedstock treated (metals in the form of sulphides and coke) are accumulated, up to very high levels, and a hot gas stripping section of the reaction liquid, designed in relation to the type of reactor adopted, for the direct and continuous removal of the conversion products, including high-boiling products.