The content of pilocarpine nitrate in eye drops and its degradation products were determined by HPLC and the stability of pilocarpine eye drops was examinedA Shim-pack Clc-Phenye column (0.15 m x 6.0 mm) was used and the detection was at 230 nm.O-Phthalic acid was used as the internal standardThe mobile phase was MeCN-5% KH2PO4 (6:100) and the pH was adjusted by H3PO4 to 3.0.The influence of light and pH on the stability of pilocarpine nitrate eye drops was studied, and pH 4.5 was the optimum one.The average recovery was 100.5 with RSD 0.6.The method was simple and specific.