Objective To observe the influence of cisplan on the expression of B7-H1 in retinoblastoma (RB) cells，and to investigate its mechanism. Methods Human RB cell line HXO-Rb44 cells were treated by 6 different concentrations of cisplan (0.000, 0.375, 0.750, 1.500, 3.000, 6.000 mu;g/ml), and their B7-H1 mRNA expression was determined by the reversetranscription polymerase chain reaction (RT-PCR) and fluorescence quantitative PCR (FQ-PCR); the B7-H1 protein expression was determined by immunofluorescence and flow cytometry. HXO-Rb44 cells were treated by 1.5 mu;g/ml cisplan for 0, 15, 30, 60, 120 min, then the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) was detected by Western blot.Results The expression of B7-H1 mRNA and protein in the 0.375, 0.750, 1.500, 3.000, 6.000 mu;g/ml group were significantly higher than that of the blank control group (F=395.478，112.03; P=0.000）. Western blot showed that cisplan (1.5 mu;g/ml) could activate ERK1/2 by increasing its phosphorylation in HXO-Rb44 cells. After cisplan treatment, the phosphorylation of ERK1/2 increased gradually and reached its peak at 30 min, and then went down gradually.Conclusion Cisplan can promote the expression of B7-H1 and activate ERK1/2 in RB cells.