The rDNA-ITS2 gene was used to investigate genetic structure and differentiation among populations of Pergande, Frankliniella occidentalis（Pergande） , in Yunnan Province. 112 rDNA-ITS2 sequences were analyzed, including 59 variable sites, defining 30 haplotypes. Haplotype diversity was quite high (Hd=0.90219) overall but nucleotide diversity was low (Pi=0.00891). The Fst value was 0.00809 and gene flow was Nm=30.64 among all populations. These results suggest that genetic differentiation was low and that gene flow between different geographic populations was sufficient. Neutral test and mismatch analysis indicate that F. occidentalis has undergone a recent population expansion. The results of AMOVA also suggest that observed genetic differences mainly originate from interpopulation differences, with relative little genetic variation within populations. These molecular data are consistent with the recent invasion of Yunnan by F. occidentalis.