Abstract: A method of determination of cyclosporine A by HPLC was proposed. Agilent Extend C18 (250 mm×4.6 mm, 5 μm) was used as stationary phase, and a mixture of acetonitrile, water, tert-butyl methyl ether and phosphoric acid (mixed in the ratio of 500 to 500 to 50 to 1) was used as mobile phase. UV-detection at 210 nm was adopted in the determination. Linear relationship between values of peak area and mass concentration of cyclosporine A was kept in the range of 0.025-2.00 g·L-1. The proposed method was used in the analysis of raw medicine of cyclosporine, values of recovery found by standard addition method were in range of 99.3%-101% with RSD (n=6) less than 1.0%.