Abstract: A specimen of psoralen, extracted from Psoralea orylifolia L. and recrystaliized from ethanol, was analysed by the polarographic method. Owing to the low solubility of psoralen in water, a 0.5M solution of lithium chloride in 80% ethanol containing 0.01% gelatin was used for the base electrolyte. A linear relationship was found to exist between the polarographic current and the concentration of psoralen within the range of 4.8×10^-4M to 6.4×10^-3M. The manually registered half-wave potential, after correction for IR drop in the cell circuit, was-1.58 V (vs. S. C. E.) at 25℃. The polarographic current was diffusion controlled and only one electron was transferred in the electrode process. The polarographic method is simple and dependable, and can be recommended for pharmaceutical analysis.