Optimization of the Technology of Chlorogenic Acid Extraction from Yacon (Smallanthus Sonchifolius) using Box-Behnken Design In order to further enhance the value of comprehensive utilization, soxhlet extraction of chlorogenic acid (CGA) from yacon was studied in this paper. Firstly, single factor experiment provided the extraction effects of three main parameters of soxhlet extraction process involving syphon time, ethanol concentration and liquid-solid rate and obtained preliminary process parameters for higher extraction rate; furthermore, Box-Behnken design was applied to obtain the three optimal parameters of extraction process and formulate a regression model fitting process parameters and extraction rate. Results showed that the optimal soxhlet extraction process was as follows: syphon times of 5, ethanol concentration of 50% and liquid-solid rate of 15 mL/g, and the predicted extraction rate was 5.21%. In the optimal process actual extraction rate was 5.22%, which accorded well with the predicted value of the model. The analysis of regression model revealed that the effect of syphon time, ethanol concentration and liquid-solid rate each other was significant, especially the interaction of ethanol concentration and liquid-solid rate was extremely significant. To sum up, response surface methodology can be applied to the optimization of soxhlet extraction process of CGA in yacon, and the optimal soxhlet extraction process is advisable to extract CGA in yanco with high extraction rate and further to enlighten industry production and market-oriented utilization of CGA.