To visualize the relationship between the collector current and source-drain voltage in the SiGe/Si chare injection transistor (CHINT), the mathematical model of this device is set up by using the tunnel model of two-dimensional hole gas(2DHG)in SiGe/Si quantum well. Then the model is simulated by MATLAB, the result shows that the drain current shows strong negative differential resistance when VDS is about 1.5V, which is in accordance with the results of the other papers.