Abstract After the ban against private-owned gas service stations was lifted in 1987, some domestic trading firms took advantage of the special feature of gasoline products as well as Taiwan¡¦s unique oil price structure to import low-quality oil products for blending into gasoline-equivalent products, which would then be sold to independent service station owners mushrooming in accordance with the oil market deregulation. According to the statistics of import/export at Taiwan customs and the comparison between supply and demand of relative industries, it is agreed that an annual total of approximate 400,000 kiloliters of various imported oil products would be blended into gasoline or diesels for sale. Moreover, as Taiwan government has been continuously providing a 14% oil price subsidy against a sluggish fishing industry caused by depleting fishing resources, the fishing fuels in glut, at an estimate of 410, 000 kiloliters a year, would be illegally sold as diesel in domestic gas service stations for higher profits. These practices have not only directly affected tax revenues of local governments, but also infringed upon the legal rights of petroleum refineries, putting the orderliness of petroleum production and sale in jeopardy. In addition, as such illicit practices are usually carried out near makeshift storage tanks with ineligible filling facilities, they have posed great threats to public safety and environment. As it is difficult to detect and thereby root out the underground transactions of such inferior gasoline and diesels, the police that was authorized insufficiently on legal aspects would carry out inspections at key roads and intersections only passively, which has posed but limited intimidation over illegal transactions of unqualified gasoline products. Realizing the facts, this survey takes the historical data on relative factors and market survey figures as basis for calculation and analysis, which is used then to assume the normal demand of gasoline and diesel markets and to establish a conclusive alarming model for flow direction. Besides, it obtains affecting variables such as market segmentation, channel characteristics, customer behaviors, price gap and business environments through interviews and questionnaires, to determine limits on the alarming model and the alarming value. Comparing with the actual consumption of gasoline and diesels, we can then judge if there remains any abnormality concerning the sales volume of gasoline and diesels. If any abnormal sign shown, we can check the alarming model item by item for timely management and control, so as to supervise and check the underground transactions of inferior gasoline and diesels. We also hope that the survey report on ¡§the Alarming Model over the Flow of Inferior Gasoline and Diesels and Its Application¡¨ could provide practical references for the detection and elimination of inferior gasoline and diesels so that the illicit and unsafe practice could be inhibited once and for all.