In order to develop suitable catalyst for hydroconversion of heavy hydrocarbon materials, possibility of high quality catalyst production from iron sulfates was pursued on the hydroconversion of 1-methylnaphthalene (1-MN). Catalytic activities of iron sulfates were very low in the absence of sulfur (S). Hydrogenation activity of ferrous sulfate dramatically increased with addition of S, Activity of ferric sulfate, however, did not increase with addition of S. From XRD analysis of catalysts recovered after the reaction, it indicated that ferrous sulfate was transformed to pyrrhotites Fe1-xS above 350 degrees C in the presence of enough S. But ferric sulfate was not transformed to pyrrhotites easily. Effect of reaction temperature and additive effects of S, presulfiding temperature and sulfuric acid to the activity, selectivity and structure of iron sulfates were investigated in detail. From results of 1-MN hydroconversion, ferrous sulfate is revealed one of useful catalyst precursors for hydrogenation of aromatic hydrocarbon.