Abstract: To establish assaying measures of diclofenac sodium sustained-release tablets, a series of experiments were performed in phosphate release medium at pH 6.8, including determining maximum absorption wave, drawing standard curve, pricision test, stability test and recovery test. The dissolution of diclofenac sodium sustained-release tablets from two different pharmaceutical factories was tested. The cumulative dissolution ratio was calculated, and the release parameters T50，Td and m were calculated by weibull equation and analyzed by variance analysis. The test result showed that the dissolution of diclofenac sodium sustained-release tablets from A factory was different from B factory, and the striking difference existed in the release parameters of sustained-release tablets from two different factories (P< 0.01). Therefore, it should be pay attention to that the quality of diclofenac sodium sustained-release tablets may vary greatly in different factories in clinical application.