Abstract: A conversion process of hydrocarbon oils comprises at least a hydrodemercaptanization process, wherein said hydrodemercaptanization process comprises contacting a feedstock with a hydrofining catalyst containing a tungsten oxide and/or a molybdenum oxide, a nickel oxide and a cobalt oxide supported on an alumina under the conditions of hydrodemercaptanization, in which the content of said tungsten oxide and/or molybdenum oxide is from 4 wt % to less than 10 wt %, the nickel oxide content is 1-5 wt %, the cobalt oxide content is 0.01-1 wt % based on the catalyst, and the ratio of total atom number of nickel and cobalt to total atom number of nickel, cobalt, tungsten and/or molybdenum is 0.3-0.9. Said process can be carried out at a lower temperature and a lower H/oil volume ratio.