The invention concerns a process for slurry phase hydroconversion of liquid sulphur-containing heavy hydrocarbon feeds, in the presence of hydrogen and in the presence of a solid catalyst, said catalyst being obtained from an aqueous solution formed from at least one cobalt and/or nickel salt of at least one heteropolyanion combining molybdenum and cobalt or molybdenum and nickel in its structure. The aqueous solution is introduced into a hydrocarbon oil containing asphaltenes and/or resins to form an emulsion and said emulsion is then injected upstream or directly into the slurry reactor.