Abstract: On the basis of single-factor test, the conditions by steam distillation for the extraction of essential oil from Herba Moslae were optimized through central composite rotatable design (CCRD) and response surface methodology (RSM). The mathematical regression model was established about the dependent variable (the extraction rate of essential oil) and indepen- dent variables ( ratio of liquid to solid, soaking time and distillation time). According to this model, the optimum extraction conditions are determined liquid to solid ratio 11.6, soaking time 73 min and distillation time 301 min. The response value (the extraction rate of essential oil )to these optimum values is 1.70%±0.03% (n=3) .

Key words: Herba Moslae, essential oil, extraction, response surface methodology