Objective The quantitative characteristics of sainfoin are easily affected by environmental conditions. In order to successfully carry out the DUS test of sainfoin, it is necessary to properly grade the expression status of quantitative characteristics.

Methods Following the sainfoin DUS test guideline, 13 quantitative characteristics of 76 sainfoin germplasm resources were observed, and the expression status of each quantitative characteristic was reasonably graded.

Results The variation range of 13 quantitative characteristics was from 6.36% to 70.58%. By using the least significant difference method, the pod length was divided into 3 grades, the number of leaflets, the compound leaf length and the spike length were divided into 5 grades, the internode length and the pod width were divided into 7 grades, and the plant height and 100 grain weight were divided into 9 grades. Using the range method, the branching was divided into 7 grades, and the flowering stage, stem diameter, blade length and blade width were divided into 9 grades. Through cluster analysis, 76 sainfoin resources could be divided into 3 major taxa. Taxa I contained 18 materials, accounting for 24%; taxa II contained 23 materials, accounting for 30%; and taxa III contained 35 materials, accounting for 46%.

Conclusion This study established a preliminary classification index for the 13 quantitative characteristics of sainfoin germplasm resources which has provided a scientific basis for the DUS testing of sainfoin in China.