The driving torque of the oscillating slat shovel harvesting device is determined by four groups of single torque coupling, and the maximum driving torque and torque fluctuation directly affect the power matching and effective power output of the tractor. Analytical equations and discrete element simulation were used to analyze the characteristics of the driving torque waveform of the harvesting device. The single torque showed a double peak per cycle and the strength of adjacent cycles. Due to the vibration balance between groups and soil viscoplasticity, the driving torque showed a double peak per cycle and a slight change in adjacent cycles. The peak value was about 1.2~2.3 times of the single torque. The maximum driving torque, torque fluctuation and specific power consumption were taken as the driving torque characteristics and influencing factors of the harvesting device. Based on the force analysis of the working monomer, the monomer torque, driving torque and specific power consumption were established as the indexes, and the four-factor and three-level Box-Behnken simulation experiment was carried out. The experimental results showed that the amplitude, vibration frequency, excavation depth, forward speed, and the interaction term between amplitude and vibration frequency had significant influence on the maximum driving torque. Under the fixed working condition, when the amplitude was 8~10mm and the vibration frequency was 8~9.67Hz, the maximum driving torque had a better value. The vibration frequency, excavation depth and their interaction were the main factors affecting the torque ripple. Under fixed conditions, when the vibration frequency was 8.67~10.67Hz, the torque ripple had a better value, and the excavation depth can be 350~450mm. The vibration frequency, amplitude, forward velocity, excavation depth, and the interaction term between vibration frequency and forward velocity were the most important factors affecting the specific power consumption. Under fixed conditions, when the forward velocity was 0.35~0.45m/s, and the vibration frequency was 7.67~9.67Hz, there was a numerical optimal value of specific power consumption. The field test results of liquorice harvester showed that when the excavation depth was 450~500mm (condition 1), the driving torque showed a double peak per cycle and the adjacent strength changed, the maximum driving torque was 797.17N·m, the torque fluctuation was 2.54, the specific power consumption was 122.06kJ/m3, and the liquorice harvest rate was 96.42%. With the excavation depth reduced to 350~400mm (condition 2), the strong and weak cycles of driving torque were not obvious. Compared with condition 1, the maximum driving torque was decreased by about 39.44%, and the torque fluctuation was decreased by about 27.95%, and the specific power consumption was basically the same. The oscillating slat shovel harvesting device had good torque balance ability, which can provide reference for the research on vibration drag reduction and energy saving harvesting of rhizome crops, especially deep rhizome crops harvesting equipment.