Abstract: Abstract: 11 primers were selected from 100 ISSR primers. 107 DNA fragments were amplified from 65 samples and each primers result in 9.72 DNA fragments. 102 fragments were polymorphic (percentage of polymorphic bands was 93.5%). The value of Nei’s genetic variations indexes of 65 cultivars based on the ISSR data varied from 0.40 to 0.65, suggesting that the genetic diversity among pakchoi cultivars is long. Cluster analysis with UPGMA method showed that the cultivars tested in this study could be divided into four groups. The results have connection with regions of cultivars origin. The results indicated that ISSR technique has better stability than RAPD , and is useful in revealing the genetic diversity and genetic relationships among packhoi species , providing a scientific basis for genetic research and packhoi breeding , as well as for gene cloning of plant germplasm and parents selection in constructing genetic linkage map of packhoi.