Commelina communis (Asiatic dayflower) is a troublesome weed in China.  Genetic variation of 46 C. communis populations from different collection sites in our country was investigated using 12 simple sequence repeat (SSR) primer pairs.  Polymorphism analysis results showed high level of genetic diversity among these populations.  The alleles (bands) were amplified by these primer pairs.  The polymorphic proportion was 18.25%, and the average polymorphism information content was 0.1330.  The highest effective number of alleles was 1.9915 at locus YP33, and the lowest value was 1.0000 at both loci YP25 and YP31.  C. communis showed major average observed heterozygosity value (0.8655) than that of average expected heterozygosity (0.1330).  C. communis populations were divided into three groups on the basis of unweighted pair-group method with arithmetic mean cluster analysis (Dice genetic similarity coefficient=0.772) and genetic structure analysis (K=3), and a principal coordinate analysis.  The results of this study further illustrated that C. communis populations contained abundant genetic information, and the 12 SSR markers could detect the microsatellite loci of C. communis genomic DNA.  These results might indicate that C. communis maintains high genetic diversity among different populations.