Thiols in RFCC naphthas produced in two refineries in China have been separated and characterized with GC/FPD. The identification results show that there are more than 20 kinds of thiols, including C3-C8 normal thiols, isothiols, thiophenol and methylthiophenol presenting in presweetening RFCC naphthas, while in sweetened RFCC naphthas, only have the isothiols and C7-C8 normal thiols been detected. The content of C7-C8 thiols and isothiols is higher in RFCC naphthas than that in FCC naphthas. [ABSTRACT FROM AUTHOR]