Abstract: Mitochondrial DNA marker has been applied in genetic structure and phylogenetic analysis, but the differences between nuclear mitochondrial pseudogenes (Numts) and mitochondrial DNA complicate phylogenetic analysis. Using the universal and special primers, 34 pseudogene sequences (Numts) and 5 real mtDNA COI sequences were amplified respectively from 34 individuals of Scylla paramamosain from the coast of southeast China. Twenty-nine haplotypes were identified and two groups (GroupⅠand GroupⅡ) were determined according to the homology of the 34 pseudogene sequences. Two insertions and an 8-bp deletion were found in some sequences of GroupⅠ, but no indel (insertion and deletion) was found in GroupⅡ. Compared to mtDNA COI sequences, the two groups had their conservative sites respectively. At least two independent nuclear transfer events are required to explain the codon position biases revealed through the pairwise comparisons of the 34 Numts, one for GroupⅠand one for GroupⅡ. The results showed the necessity of great care in interpreting PCR-generated mtDNA sequences using universal primers when used in population or evolutionary studies in genus Scylla.