363 clones of Populus deltoides were used as test materials. Based on 20 pairs of SSR molecular marker amplification data, 10%, 15%, 20%, 25%, 30%, 35% and 40% sampling ratios were set to construct the primary core collection of P. deltoides. The validity of the core collection was supported by ttest using genetic parameters such as the average number of observed alleles (Na). Retention ratio of genetic diversity such as average observed allele number (Na) between core collection, reserve collection and original collection, and the core collection was further confirmed by the PCoA analysis. The results were described as follows: (1) A total of 278 polymorphic loci was detected by 20 pairs of SSR primers. The genetic diversity parameters I and H were 1.667 and 0.688 2, respectively, indicating that the southern type of P. deltoides germplasm resources were rich in genetic variation. （2） Comparing the average Na, I and H changes to determine the optimal sampling ratio of 15%, obtaining 54 core collections and 309 reserve collection, ttest analysis suggested that there was not a significant correlation between average Na, I and H of primary core collection and the original collection (P> 0.05), except for the average Na, the retaining ratios of Ne, Ho, I and H was 111%, 105%, 104% and 104%, respectively. （3）Principal coordinate analysis (PCoA) showed that the primary core collection was not only similar to the original germplasm distribution, but also distributed uniformly and comprehensively, which could represent the geometric distribution of the original germplasm in the figure. These results demonstrated that the 45 accessions as primary core collection could preserved most of the alleles and genotypes of the original germplasm, Some genetic diversity indexes increase while the genetic redundancy and genetic repetition was removed，which mean that the primary core collection could stand for original collection excellently.