Whole genome sequencing of 9 type I circulating vaccine-derived polioviruses (cVDPVs) isolated in Guizhou Province in China revealed that reverse mutations did not occur in G-480 and U-525 which are known as the most important neurovirulence determinate sites, while other known neurovirulence determinate sites such as A-2438, A-2795, C-6203 and G-7441 did revert to Mahoney type. 5 type I cVDPVs were selected for neurovirulence test on PVR-Tg21 transgenic mice which express human poliovirus receptor gene based on their different nucleotide sequences, they all showed higher neurovirulence than P1/Sabin strain, and the neurovirulence of CHN8184 and CHN8229-1. 1 were comparable to that of wild type P1/Mahoney. The neurovirulence of CHN8229-1.1, CHN8229-2 and CHN8229-3 presented a trend of decreasing, but still laid in high level. There were 7 nucleotide mutations between CHN8229-1.1 and CHN8229-2, and only 2 between CHN8229-2 and CHN8229-3 in their whole genomes, but the neurovirulence among them were relatively different, showing that there must be some unknown neurovirulence determinate sites among these mutations. Computer predicted RNA secondary structure of stem-loop V of the poliovirus 5' NCR of Guizhou type I cVDPVs was relatively stable. In the situation that no reverse mutation occurred in G-480, some type I cVDPVs already showed high neurovirulence nearly equal to P1/Mahoney, it meant that the effect of G-480 point mutation that determined neurovirulence of P1/Sabin strain has been overestimated, G-480 was not the only important site to determine neurovirulence in P1/Sabin strain, others also may play the very important role. More details are needed to elucidate the mechanism of attenuation in type I polioviruses.