【Background】As a notorious invasive species, the red imported fire ant (Solenopsis invicta) has important economic consequences as it causes losses to households and businesses including agriculture since its introduction in China. However, little is now about the sources of introduced populations and their entry paths. 【Method】The genetic diversity of 15 populations of S.invicta collected from 14 regions in China and one from United States of America were investigated using microsatellite molecular marker SSR (simple sequence repeat). 【Result】Two to six alleles were found at each microsatellite locus (total 28 alleles at seven loci). The mean observed heterozygosity (HO) and expected heterozygosity (HE) were consistent with Hardy-Weinberg equilibrium. A medium level of genetic diversity was revealed: HO=0.2848, HE=0.2708, I=0.3174, Nei′s=0.2629 and P=43.63%. The mean genetic differentiation index FST was 0.4258, indicating that 42.58% of the total molecular variance was attributable to population divergence. The high level of genetic differentiation might be caused by geographic isolation and barriers to gene flow (Nem=0.7442). The genetic distance D showed that the genetic distances between Heyuan population and the other populations was relatively higher than any other two populations, suggesting that Heyuan population might be the original source among all the Chinese populations. On the basis of UPGMA cluster analysis, genetic differentiation was mainly due to geographic separation and trade movement. 【Conclusion and significance】Based on our results, there was a significant relationship between genetic distance and geographic distance for close populations but not for populations far apart. The results suggest that monitoring or quarantine programs targeting source areas or key transportation routes are crucial for long distance invasion events.