Although the caustic sulfur components in LPG have been removed, the process converted the result of copper strip corrosion test from passing into failing sometimes still happens when the LPGs are stored in tanks for several days in some refineries. By analyzing the sulfur species in LPGs that passed and failed in copper strip corrosion test with GC- FPD and GC- MS, It was found that hydrogen sulfide and methanethiol were the main corrosive components. The partial conversion of dimethyl disulfide is the source of hydrogen sulfide and methanethiol in LPG.