The present invention is a method and system for simulating the aging process of a circuit. A two-step process is employed whereby, in a first simulation step, a simulation is conducted to obtain node voltages for the original circuit and the node voltages are stored in a file. In the second step, a subsequent simulation is run after transistors of the circuit are replaced by aging subcircuits, which contain aging models, and initial node voltages are updated. A script is used to set the bias voltage inputs for the aging models using the node voltages stored in the file from the first step. With more accurate bias voltage inputs for the aging models, the aging simulations are conducted to compute the circuit degradation.