To determine the chlorogenic acid content in Lycium barbarum L. by HPLC (Reversed Phase Highperformance Liquid Chromatography); and to observe the protective effect of Lycium barbarum L. extract on Retinal Ganglion Cells (RGCs) in rats with ocular hypertension. A rat model of chronic ocular hypertension was established using healthy adult rats. The rats were randomized into the model group and the treatment group. The effects of Lycium barbarum L. extract on Intraocular Pressure (IOP), multifocal Electroretinogram (mfERG), apoptosis of RGCs and retinal Nitric Oxide (NO) content of rats with ocular hypertension were observed. The average recovery of chlorogenic acid was 100.1%, RSD=0.9%. Chlorogenic acid content in Lycium barbarum L. extract was 40.71 mg/g. Lycium barbarum L. extract could effectively prevent the elevation of IOP; improve the rat mfERG; significantly lower the retinal NO content in rats; and reduce the apoptosis of RGCs. Lycium barbarum L. extract has a protective effect on RGCs in rats with ocular hypertension. The proposed HPLC method is simple, accurate and reproducible, which can be used as the mass control standard of Lycium barbarum L. extract.