Abstract： 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 μg/ml),and their B7-H1 mRNA expression was determined by the reverse-transcription 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 μg/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 μg/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 (1.5μg/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.