Hg-based (Hg,M)-1222 cuprates (Hg 0 . 7 5 M 0 . 2 5 )Sr 2 (Gd 1 . 5 Ce 0 . 5 )Cu 2 O z (M=W, Mo, V, Cr, Ti) have been synthesized using the precursor Sr 2 (Gd 1 . 5 Ce 0 . 5 )Cu 2 O z prepared by solid state reaction and citrate sol-gel process, respectively. X-ray powder diffraction indicates that the samples prepared by sol-gel process have better crystallization comparing with the solid state reaction. The citrate sol-gel process was improved by using diffluent Ce(NO 3 ) 3 to replace CeO 2 which is almost insoluble in nitric acid and pure (Hg,M)-1222 phase was obtained. Superconductivity was observed in the (Hg 0 . 7 5 M 0 . 2 5 )Sr 2 (Gd 1 . 5 Ce 0 . 5 )Cu 2 O z phase with M=W, Mo. Annealing under high oxygen pressure has apparently decreased the resistivity and improved T c for (Hg,M)-1222 (M=W, Mo) samples.