OBJECTIVE:To prepare diclofenac sodium controlled release tablet,and to evaluate the mechanism of drug release.METHODS:Stearic acid and ethyl cellulose were used as blocking agents and sodium carboxylmethyl starch was used as disintegrating agent.Tablets were made after drying the granules prepared.The dissolution rates were acquired according to Chinese Pharmacopoeia(1995).RESULTS:Drug release from the tablets prepared was of zero-order release before 90% of drug released.No significant influences were observed from the dissolution rates of the different pressure of tablet(5～10kg),amount of drugs contained in the tablet(35%～60%)and different geometry of the tablets,respectively.The remarkable difference waw observed between the disintegrating and blocking agents contained in the tablets.CONCLUSION:The time of 50% of durg released could be changed as the amount of disintegrating or blocking agents were changed.