Aim To investigate the effect of 9-cis-retinoid acid (9-cisRA), a specific agonist of retinoid X receptors (RXR) on the differentiation of THP-1 human monocyte cell induced by phorbol-12-myristate-13-acetate (PMA). Methods Human monocyte cell line THP-1 was cultured and induced to macrophage by PMA treatment. The effect of 9-cisRA on the differentiation induced by PMA was studied. Cell morphology was observed by phase contrast microscope and the adhesion rate of THP-1 was detected by methyl thiazolyltetrazolium (MTT) assay. The cell surface markers involved in differentiation of monocyte/macrophage (CD11b, CD36) were analyzed by flow cytometry (FACS). Results The metamorphotic cells were decreased in 9-cisRA group. THP-1 cell adhesion rate was inhibited by 50% (P<0.01), and the cell surface markers (CD11b, CD36) were decreased by 50% and 28% (P<0.01) in 9-cisRA treated group. Conclusion The specific agonist of RXR, 9-cisRA could effectively inhibit the differentiation of THP-1 human monocyte induced by PMA.