Terahertz imaging provided a good contrast between skin cancer (basal cell carcinoma BCC) and healthy tissue owing to the high water content and strong absorption of cancer tissue at THz frequencies. By this method we can approximately diagnose skin cancer tissues. In this letter, the healthy skin and BCC were modeled as Double Debye dispersive media and the model was incorporated into the FDTD method to simulate the propagation of a THz pulse.