To study the optimal process conditions and the mass transfer kinetic model of the extraction process,the Plackett Burman test,the steepest climbing test and the Box Behnken response surface method were used to optimize the key process parameters of ultrasonic-assisted deep eutectic solvent extraction of synephrine from Aurantii Fructus Immaturus.Based on Fick′s second law,the extraction kinetic model was established for the extraction of synephrine from Aurantii Fructus Immaturus with ultrasonic assisted deep eutectic solvent extraction.By measuring the mass concentration of synephrine in the extraction solution at different power and extraction time,the model was fitted and verified,and the corresponding kinetic parameters were solved.The results showed that the optimal extraction solvent was the deep eutectic solvent composed of betaine monohydrate and lactic acid (molar ratio 1∶3,water content 50%).The optimal process was as follows:the liquid material ratio was 39 mL /g,ultrasonic power was 220 W,ultrasonic time was 20 min.Under these conditions,the yield of synephrine was 0.428 4%,which was close to the predicted value of the model,and better than the traditional water reflux extraction method,85% ethanol reflux extraction method,ultrasonic assisted 14% ethanol extraction method,ultrasound assisted 70% methanol extraction method and ultrasound-assisted water extraction method.The kinetic general equation and exponential equation obtained by fitting the kinetic experimental data have a good correlation with the kinetic model.The corresponding kinetic parameters such as rate constant,relative extraction rate were calculated,and the regression equation of half-life and effective diffusion coefficient has been obtained by fitting,which provides data reference for the optimization of the extraction process and in-depth theoretical research of Aurantii Fructus Immaturus.