333 accessions of Saccharum spontaneum L. from Guangxi were used to mine the excellent wild genetic resources for sugarcane breeding. The data from 12 pairs of SSR primers and 28 phenotypic traits were used to construct the core germplasm and conduct association analysis of Saccharum spontaneum L. in Guangxi. The results of association analysis showed that 5 phenotypic traits including the stem diameter， the internode length， the color before exposure， defoliation and hairiness were significantly correlated with 8 SSR loci. The diameter of stem was significantly correlated with leaf length， leaf width， internode length， number of nodes and brix. There was a significant to extremely significant positive correlation between the 4 phenotypic traits including the plant height， stem diameter， internode length， and number of nodes. The brix was negatively correlated with stem diameter and internode length. Core germplasm sampling was subjected to gradient screening based on the proportion of total resources at 0.1， 0.2， 0.3， 0.4， 0.5， 0.6， 0.7， 0.8， and 0.9. When the sampling ratio reached 30% or more， it covered 100% allele. The results of evaluating genetic diversity and principal component analysis showed that the screened materials for constructing the core germplasm of Saccharum spontaneum L. had rich genetic diversity， and the principal component map drawn based on the core germplasm was consistent with the distribution map of the original germplasm. It is indicated that the core germplasm of Saccharum spontaneum L. constructed with 99 selected samples based on a sampling ratio of 30% has good representativeness by evaluating genetic diversity and principal component analysis.