Abstract: In order to explore the effect of hulling conditions on the mechanical properties of rice grains,five kinds of japonica rice and five kinds of indica rice were used as raw materials,and the different gap-thickness ratio and the whitening time were investigated.Additionally,the rice hulling and brown rice whitening tests were carried out respectively.The mechanical properties of grain after hulling and whitening were measured,and the changes of grain crushing force after hulling and whitening were analyzed.The results showed that the mechanical properties of brown rice had a decrease trend with the reducing of the gap-thickness ratio,and the influence of the gap-thickness ratio on the compressive force was significant,and the influence on the shear crushing force and the three-point bending and crushing force was smaller.The effect of compressive force was larger,and the effect of shear crushing force and three-point bending and crushing force was smaller.The crushing force of head rice grain decreased with the increase of whitening time.The crushing force of japonica rice decreased with the increase of the whitening time,and the compressive force and shear crushing force were influenced by the varieties.The three-point bending and crushing force was less affected by different kinds of the cultivars.After the whitening time was more than 60 seconds,the 3 kinds of crushing force decreased rapidly,and the difference between varieties had a great influence on the compressive force and shear crushing force,which had little effect on the bending strength of the three points.Therefore,the three-point bending force can be used to guide the reasonable adjustment of rice milling process parameters to reduce the broken rice yield.