Operational amplifier is the basis of analog circuit technology, whose reliability is very important for circuit system. In order to collect parameters online and to assess working life of operational amplifier, a parameters online testing system was designed. This system is consisted of a typical operating circuit and a electrical connection of the test circuit for device under test(DUT). Besides, parameters which are tested by the test circuit can be collected by a data acquisition system. And values of parameters can be displayed on Pc. And an accelerated degradation test(ADT) is designed, a heat source and thermocouple were pasted on the back of the heat sink so that the temperature of heat source can be controlled. Finally, the life of this operational amplifier operating under normal stresses can be assessed by mathematical methods. The results indicate that the proposed method is valid for online life assessment of operational amplifier.