Abstract: This paper deals With the pattern of release of propafenone hydrochloride(PF),diltiazem hydrochloride(DH)and isosorbide dinitrate(ID)from matrices of sodium alginate(NaAlg)with different molecular weights.The results revealed that the molecular weight of NaAlg wasinversely proportional to the release rate of these drugs.According to the above relationship,therelease rate of drugs from NaAlg with any molecular weight can be predicted,This result mightprovide a theoretical consideration for formulation design of sustained release preparations andespecially for the applieation of NaAlg。