In order to achieve better operating type and optimal working parameters for the roots-soil separation, experiments under different working modes which include compacting, hitting, vibrating and the combination of above methods were performed by employing the test-bed of fibrous root crops. The experimental results showed that the better separation method can be obtained for the roots-soil complex with low moisture content by the combination of compacting and hitting method. Furthermore, experiments based on Box-Behnken experimental design method were performed for optimizing parameters. The roots-soil separation rate and power consumption were considered as the performance index, and the parameters including roll clearance, revolving speed of hammer, mass of hammer were selected as the independent parameters. The mathematical model corresponding to the roots-soil separation rate and power consumption was established. By the analysis of the interaction between the performance index and the independent parameters, multi-objective optimization for the mathematical model was obtained. The value of the optimal working parameters were as following: roll clearance of 22 mm, revolving speed of hammer of 200 r/min and mass of hammer of 0.3 kg, respectively. The roots-soil separation rate of 95.44% and power consumption of 0.72 kW were obtained by experiment, which were in accordance with the theoretical prediction. It was concluded that better separation rate could be obtained by employing the combination of compacting and hitting method.