Propane and butane as LPG product containing undesirable sulfur compound which are causing a nasty smell of the product and bad copper plate corrosion. Decreasing of sulfur content tend to sale cost increasing. Total sulfur content of liquefied Petroleum product from a gas refineries located in south pars (south of Iran) presents fluctuation and off specification product occasionally. In this paper we intend to investigate and analyze the results obtained and describe the effects of important parameters on critical point of de-mercaptanization process. Also some modification is presented, based on data field, to decline the total sulfur of product and performance enhancement of process.