ISA206 was used to obtain the vaccine by emulsifying 4-hydroxy-3-nitrophenylacetyl conjugated chicken egg white protein （NP-OVA） with immunopotentiator CVC1302 to study the immune mechanism of CVC1302 regulating the occurrence of somatic hypermutation in germinal center B （GC B） cells. Six-week-old BALB/c female mice were divided into 2 groups and immunized with NP-CVC1302-ISA206， NP-ISA206 in the hind leg muscles， with each mouse receiving 100 μL vaccine and 50 μg NP-OVA. Germinal center B cells were obtained with flow cytometry after14 days of immunization， and the variable region VH_186.2 gene sequence of immunoglobulin in GC B cells was amplified with nested-PCR. Western blot was used to detect the expression level of cytidine deaminase （AID） and Pax5 induced activation， and the differences in the expression level of AID and Pax5 between groups were compared with β-actin as an internal reference. The transcription level of AID and Pax5 in GC B cells was analyzed with fluorescence quantitative PCR. The results showed that immunopotentiator CVC1302 significantly induced the mutation frequency of VH_186.2 in the immunoglobulin sequence of germinal center B cells， with a W33L mutation frequency of 62.2% in the NP-CVC1302 immunized group and only 20.25% in the NP immunized group. CVC1302 increased the expression level of AID protein and Pax5 protein in GC B cells. The relative expression level of AID protein in the NP-CVC1302 immunized group was 0.72， while that in the NP immunized group was only 0.16. The relative expression level of Pax5 protein in the NP-CVC1302 immunized group was 0.62， while that in the NP immunized group was only 0.26. CVC1302 enhanced the transcription level of AID gene and Pax5 gene in the NP-CVC1302 immunized group， which was increased by 2.36 and 4.13 times compared to that in the NP immunized group. It is indicated that CVC1302 relies on Pax5 mediated AID expression to regulate the occurrence of somatic hypermutation in germinal center B cells.