Abstract: To effectively control the risk in flue-cured tobacco purchasing and extend purchasing process management method, the curve representing tobacco purchasing risk was plotted by the aid of EXCEL. The results showed that the relationship between variables x (purchasing weeks) and y (purchasing risk index of weeks) could be represented by a parabolic curve. Higher degree polynomial curves were tested, it was found that the 3rd-degree polynomial curve was of high fitting precision and simple in calculation, which was more suitable for the establishment of mathematical model of purchasing risk.