There were reports that natural selection can influence on synonymous codon usage pattern in viruses and the same conclusions are also obtained from this study. Three evidences support this conclusion. The first evidence is that PCV genome is GC3% -poor (average value = 47.08, SD = 2.88), but most of preferentially used codons are G/ T-ended codons. Meanwhile, average of A 3 % is higher than that of T 3 %, but among the codons which PCV prefers to using, there are only three preferable codons with the end base of A 3 % while six those with the end base of T 3 %. The second evidence is that the high similarities exist between PCV and its natural host. The third evidence is that CpG and the synonymous codon including it were inhibited. The three above evidences both state that natural selection is involved in formation of PCV synonymous codon usage pattern.