A process, in which arsenic in the residue is transformed directly into scorodite and copper dissolves into the solution simultaneously, was studied. The process was carried out in acidic ferrous sulfate solution under oxygen pressure. The optimum conditions of the process were determined as follows: the initial H2SO4 concentration was 10 g/L; liquid/solid ratio was 10; Fe/As molar ratio in the feedstock was 1; the addition of calcium lignosulphonate was 1% of residue; oxygen pressure, temperature and reaction time were 1.5MPa, 150℃ and 6h respectively. Under these conditions, arsenic transformed to crystalline scorodite in size of 5-10μm, and the transformation efficiency reached 97.60%; meanwhile, the copper was leached with a high efficiency of 93.34%. The stability of the leaching residue was evaluated by TCLP testing, and the results indicated the concentration of arsenic in the leaching solution was extremely low as 0.04 mg/L and met the standard of safe stockpile.