Abstract: Objective 　To study DNA polymeraseβ(polβ) gene mutation in human nasopharyngeal cancer. Methods 　40 cases of nasopharyngeal carcinoma (NPC) tissues were collected to study DNA polβgene mutation with PT-PCR, PCR-SSCP and DNA sequence analyzing technique, the 40 cases of NPC were divided into three groups according to pathology differentiation, 16 cases of grade Ⅰ( G1), 14 cases of grade Ⅱ( G2), 10 cases of grade Ⅲ( G3) . Results 　Polβgene mutation was detected by SSCP in 13 of 40 NPC tissues (with mutation rate 32. 5 %) and Many kinds of mutation were found by DNA sequencing, the mutation rate of G1, G2, G3 was 12. 5 %, 21. 4 %, 80 % respectively. The sequencing of the PCR product showed an T to C chang at nucleotide 454, which resulted in a substitution of the amino acid from Phe to Ser at site 114 ; 466nt G→A resulting in Gly →Glu at 118 site ;148nt A →G resulting in Asn→Ser at 28 site. Conclusion 　The study proves there is polβalternation in human nasopharyngeal carcinoma, this induces change in amino acid and spatial st ructure. The mutation rate in low differentiated cancer was significantly higher than those in moderate and high ones. These mutations may be related with the development of NPC.