by another method rather than with the subsequent stage rectification tower the refined product of lpg is directly obtained only at outlet a 1 example 9 is similar to example 1 and the difference lies in that the fine desulfurization and the mercaptan conversion are conducted in one fixed bed reactor and the fixed bed reactor is preferably a fixed bed reaction tower wherein the solid catalyst bed both as desulfurizer for fine desulfurization and as catalyst bed for mercaptan conversion comprising 3cao fe 2 o 3 6h 2 o as both effective component and active component is set on the fixed bed in the reaction tower the inlet concentration of hydrogen sulfide in the lpg is less than or equal to 1000 ppm preferably less than or equal to 100 ppm the operation conditions for fine desulfurization and mercaptan conversion are temperature 10 100 u00b0 c preferably from atmospheric temperature or 30 to 60 u00b0 c pressure gauge pressure 0 4 2 5 mpa preferably 0 8 1 6 mpa liquid space rate 0 5 1 h u2212 1 loading height of the desulfurizer also as catalyst less than or equal to 10 m and ratio of height to diameter 3 1 to 6 1 the lpg flows through the desulfurizer also as catalyst bed of the fixed bed reaction tower from bottom to top wherein the resultants formed by the reaction between hydrogen sulfide and the desulfurizer also as catalyst adhere on the lower half of said bed so as to fully remove the hydrogen sulfide in the lpg when the lpg passes through the lower half of said bed and an oxidation reaction takes place between.