Abstract: This paper reports studies on the stability of cefazolin with nonisothermal kinetics method. The temperature was increased in consecutive equal steps. The kinetic equation was solved by computer. For each step, the rate constant and corresponding concentration were calculated. According to the principle of minimum sum of the squares of the difference between the experimental and the theoretical values, the corresponding activation energy is regarded as the activation energy of the reaction. The results obtained by the nonisothermal method are similar to those obtained by the long term sample observation method.