种子质量分级是制定种子质量标准的主要依据。以往多采用样本平均数方法，凭经验判断对种子纯度、净度、发芽率、水份含量等质量参数进行分级。这样分级带有很大的主观性、盲目性。分级后很难判断各级种子的代表量，对样本的统一集合平均也不作差异的合理性判断，还易出现级差 Seeding quality grading is the main basis for the development of seed quality standards. In the past, the sample average method was adopted, and the quality parameters such as seed purity, clarity, germination rate and moisture content were graded by experience. This classification with a lot of subjectivity, blindness. After classification, it is difficult to judge the representative amount of seed at all levels, and it is also easy to judge the reasonableness of the uniform collection of samples on average