Abstract: HPLC was used to determine the pilocarpine (P) content in controlled—release ophthalmic films. The stability of the films was examined with the classical constant temperature method. The use of HPLC made it possible to determine the different contents of P and its degradation products-isopilocarpine and pilocarpic acid etc. The average amount of drug recovered from the films was 100±0.6%. The results indicated that the degradation of drug in film complied with the first-order kinetic process. Besides, according to Arrhenius rule through the linear regression, the activation energy of P was 17.54 Kcal. Mol^—1. Storage period at 25℃（t^25°_0.9） was 5 months, and 3.6 years at 5℃(t^5°_0.9) , respectively. Apparently the stability of P in the film was increased substantially.