Abstract: We screened and constructed a test population consisting of 419 individuals of Paeonia rockii (S. G. Haw et L. A. Lauener) T. Hong et J. J. Li, with 12 fruit traits then analyzed. Results indicated that highly significant differences were found for all fruit traits among the different accessions. Based on correlation analysis, 51 pairs of combinations were significantly correlated, among which 46 pairs were very significantly correlated. Principal component analysis classified the 12 fruit traits into three principal components, which explained the variation of fruit traits in the test population. Systematic cluster analysis divided the test population into five categories and the 12 quantitative traits into four categories. Taken together, three grading standards for the main indicators (fruit number, fruit fresh weight, seed number, and seed fresh weight of individual plant) and secondary indicators of yield formation in P. rockii were determined, and eight individual plants with high-yield potential were obtained.