This paper investigates the causes of the slowdown of the growth of the sales volume of compact cars in the Taiwan area on the basis of the modes of fuzzy regression and traditional regression. The contents include: (a)The study of the theory and application of fuzzy regression: (b)The comparison of the characteristics of traditional regression and fuzzy regression: (c)The study and analysis of the influence of various taxes and fees on the sales volume of compact cars: and (d)The study and presentation of various suggestions regarding taxes and fees. Concrete evidence shows that the indistinct regression has an advantage of fitting the practical environment and taxes and fees account for quite a large ratio in the costs of purchasing and utilizing a passenger car. Theerfore, the adjustment method and rate greatly influence people's willingness to buy cars, Besides, under the current system, the overgrowth of the number of passenger cars is mainly due to the increase in the GNP. Thus, people's purchasing power has exceeded the burden of taxes and fees. Lastly, this research also studies the applicability and timing of levying taxes and fees, and presents the relevant implementation proposals.