Based on 0.5 μm CMOS process，a Transient Voltage Suppressor(TVS) diode is designed. Using the black box theory to build the negative operating character under high voltage and high current of the device，the curve containing the first breakdown point and the second breakdown(hardware failure) point is obtained by Matlab. In order to configure the accuracy of the model, the Silvaco TCAD(Computer Aided Design Technology) device simulation platform is adopted. The curves of two strategies are basically equal. And the model built can predict the electronic characteristic of TVS diode when suppressing transient voltage.