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A spring-tooth weeding working in paddy field was designed. Weed cutter with arc-shaped bend could reduce the injury rate of seedlings in some extent. The steel soft shaft was selected as transmission parts of the device. The quadratic rotation-orthogonal test was applied in 7 and 14 days respectively. The effects of interaction of cutter rotation speed, forward velocity of machine, buried depth on weeding ratio and seeding injury ratio were attained. The optimal combination in 7 days’ test was: the cutter rotation speed was 230r/min, the forward velocity was 1.02m/s, the buried depth was 18 mm, weeding rate was 73%, and miller injury rate was 0.13%. The optimal combination in 14 days’ test was: the cutter rotation speed was 230r/min, the forward velocity was 0.48m/s, the buried depth was 27mm. The verification test was carried on according to the optimal operational parameters combination. The results showed that this operational parameter combination could fulfils the request of weeding ratio; meanwhile, the seeding injury ratio was the lowest.