The objective of this study is to investigate the relative expression of HMG-CoA reductase (hmgr) and vitellogenin (vg) mRNA of Helicoverpa armigera adults under UV light irradiation, together with the fecundity variation of UV light irradiation group. Quantitative real-time PCR (qPCR) technique was applied to detect the expression of hmgr and vg of H.armigera of the UV light irradiation group. Total RNA was extracted from the whole body of H.armigera,and synthesized to cDNA via reverse transcription. Specific primers on hmgr,vg and β-actin in GenBank were used to carry out qPCR. In addition,this study also recorded the number of the eggs for female adults after UV light irradiation. The expression of hmgr of H.armigera significantly increased after the exposure to UV light irradiation from 0.5 h to 5.0 h, which was higher than that of control after UV light irradiation, while the vg expression increased 24 h later after UV light irradiation. The results also suggest that the fecundity of female adults significantly increased after UV treatment of 1.0 h to 4.0 h. This study is the first analysis of differentially expressed mRNAs in phototactic insects under UV light irradiation conditions and gives new insights into the adaptation mechanisms responsive to UV light irradiation stress. 