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An ellipsoid particle model was established according to the physical properties of rice grain. The discrete element method was used to simulate the impact process of a grain with a detection sensor. The results indicated that the peak normal contact force Fn max was increased with the increasing of curvature radius during the central impact process. Rotation of grain was driven during the eccentric impact process which reduced the value of Fn max. The differences of Fn max was enlarged with the increasing of grain radius ratio γ, and the minimal value of peak force ratio ηwas lower than 45% with γof 3. The asymmetric variation behavior of ηwas shown during the oblique impact process and the variation range of η was increased. The minimal value of peak force ratio ηwas about 30% with γof 3. The rise time of impact force tr was in the range of 14～26 μs. Then, a detection sensor using piezo-electric polyvinylidene fluoride (PVDF) film as sensitive material was presented and the rice grains impact tests were carried out. The results showed that the peak output voltage was fluctuated in 2～4 V, and the rise time of impact force tr was 15～35 μs. 