Background Golden snub-nosed monkeys ( Rhinopithecus roxellana ) are an endangered species in China.In the present study, the blood transcriptomes of nine monkeys were characterized by using RNA-Seq technology.Results 57.31 Gb high-quality sequencing data was obtained. The clean data of each sample was >5 Gb, and 86.17% to 94.48% of the reads of each sample could be compared to reference genome of snub-nosed monkey. After assembly, we obtained 24,992 genes, including 3,917 new genes. Many genes were up-regulated or down-regulated with age. In adult group of R. roxellana roxellana, there were 76 differential genes, including 68 up-regulated and 8 down-regulated genes, compared with the young group. While, compared with the adult group, in the old group there were 58 differential genes, including 25 up-regulated genes and 23 down-regulated genes. In R. roxellana qinlingensis , compared with the young group, 117 differential genes were obtained, including 34 up-regulated and 83 down-regulated genes. Functional enrichment analysis indicated that the up-regulated genes were mainly related to innate immune response and T-cell activity, while the down-regulated genes were mainly involved in B-cell activity, suggesting that immune competence of adult group increased gradually compared to young group. However, the adaptive immune function declined gradually in the old group.Conclusions Our findings will contribute to understand on the molecular mechanisms of age-related changes in immune system, which will provide a foundation for future study in snub-nosed monkey.