Human cytomegalovirus (HCMV) has been associated with a wide spectrum of diseases. There is currently no effective treatment for eliminating the virus. Garlic bulb extract has been reported to possess anti-viral efficacy. This study aimed to investigate the expression of the immediate-early (IE; ul122 and ul123), early (E; ul54) and late (L; ul83) genes of HCMV as well as the inhibitory effect of allitridin on the transcription levels of these genes. The results indicated that a HCMV gene expression cascade occurred, and that the deletion of IE72 had no influence on the transcription of the ul122 gene, while it led to significant reductions of ul54 and ul83 mRNA expression levels. Additionally, allitridin effectively suppressed the transcription of the HCMV IE, E and L genes; the inhibition rates of the transcription of the ul122 and ul123 genes were higher compared with those of ul54 and ul83 mRNA expression, while the expression of the IE genes was not significantly reduced by ganciclovir (GCV). Our results indicate that the HCMV IE72 deletion mutant strain affects the transcription of the virus downstream gene, allitridin inhibits HCMV infection in vitro, and that the IE genes may be the key target of allitridin in its action against HCMV.