Abstract: As a new seed moisture detection method,low field NMR has the advantages of simplicity,rapidity and non-destructive,and can realize single seed imaging.In this paper,six kinds of rice such as Xinfeng 6 Xiang,Longjing 40,Jihong,super rice,Yanfeng and Qiaoyu were used as experimental raw materials,and the low field NMR water standard curve was established by using the low field NMR instrument.The standard curve has good linearity and the correlation coefficient is greater than 0.99.The verification result is that the difference between the water measured by the national standard method and the water measured by the low field NMR method is within 0.2%,which can be considered to be in the range of 19～25 ℃,Low field NMR is suitable for the determination of water content in rice from high water content to low water content.During the experiment,it is found that the moisture measured by the national standard method will still decrease after two constant weights.If the interval between constant weights is prolonged,the weight difference between the two measurements will exceed 2 mg,and it is difficult to judge the drying end point.Therefore,it is speculated that the moisture measured by the national standard method is not the true value of the sample moisture.At the same time,this paper studies the effects of whole grain and different crushing methods on moisture measurement,as well as the effects of vertical crushing time and whole grain drying time on moisture measurement,in order to explore the true value moisture of rice,and also provide guidance for more reasonable and accurate moisture measurement and verification of low field NMR technology,which is conducive to further development and application in the later stage.The results showed that the water content of whole rice was lower than that of rice after vertical crushing,indicating that crushing would change the ratio of bound water to free water;with the increase of milling time,the bound water first increased and then decreased,and the free water gradually decreased;the true moisture of rice can not be obtained by prolonging the drying time.