Abstract: In order to optimize the determination parameters of crude oil from flue-cured tobacco leaves extracted by Soxhlet extraction,the single factor tests and a Box-Behnken design were applied to study the effects of sample weight,reflow time,and drying time on the extraction rate of crude oil. And a new UV absorption spectroscopic method of determination crude oil was established. The results showed that when the drying temperature was set at 105 ℃,the predictable optimum extraction conditions for crude oil were as follows:Sample weight 3.08 g,reflow time 6 h,and drying time 1.5 h. Under the optimum condition,the total extraction yield was 6.27%. The linear relationships between values of absorption and mass concentration of crude oil at 326 and 415 nm wavelength were good(R_{326 nm}²=0.9982,R_{415 nm}²=0.9993),with linearity ranges of 0.276~2.211 g/L(326 nm wavelength)and 0.276~2.763 g/L(415 nm wavelength). The detection limits were 0.128 and 0.093 g/L,and quantification were 0.387 and 0.281 g/L,respectively. The optimum Soxhlet extraction process and contents determination of crude fat in tobacco were established by response surface methodology and UV spectrophotometry. The method was simple,time-saving,and had good repeatability and precision,which would be suitable for analysis crude fat of batch tobacco sample.