Aiming at the problems of high leakage rate, easy congestion and difficult soil fragmentation in the root system, which lead to difficulties in subsequent sorting and separation and low efficiency of combined harvesting. The discrete element simulation method was applied to establish the root-tuber-soil discrete element model of Cyperus edulis, the mechanism of the interaction between root-tuber-soil of Cyperus edulis on the fragmentation of the root-soil annulus of Cyperus edulis was analyzed, and a reverse spin-throw type starting device was designed. The results showed that the optimum combination of parameters for the reverse rotary tiller was as follows: phase angle of 61°, installation spacing of 150mm, soil fragmentation rate of 94.10%, buried fruit rate of 1.39%, under the same parameter settings with ordinary rotary tiller combination for field verification test, the results showed that buried fruit rate was reduced by 13.33%, soil fragmentation rate was increased by 3.15%, which met the technical requirements of Chinese Cyperus edulis mechanized harvesting standards, the research results can provide a theoretical reference basis for further improvement of Cyperus edulis harvesting equipment development.