Abstract: This paper presents a multivariate linear model for predicting the stability ofpharmaceutical preparations.Any drug,which is fit for isothermal disintegrating kinetic formula andArrhenius formula,can be represented by a drug plane in three-dimensional ccordinates.Predicting thestability of drugs can be accomplished by the following steps:first,the logarithm of the time ln(t)plots against the concentration function of drugs lnf(c₀),-f(c)and the reciprocal of Kelvintemperature 1/T;second,the regression equation so obtained can be applied to calculate the activationenergy and shelf-life of drugs.The determination of the stability of tenoxicam injection, ascorbic acidinjection and tetracaine hydrochloride solution shows:the results of classical isothermal kinetic methodand those of this model agree with each other satisfactorily.The latter can reduce laboratory workgreatly and using SAS software makes data treatment much simpler.