A novel method of modified transistor model is introduced. The D-band transistor models of OMMIC D007IH and D-band Coplanar Waveguide(CPW) model are modified. The method determines dielectric constant of CPW model by simulation curve fitting. The value of CGD in the transistor models is modified by curve fitting of CGY2191UH chip S-parameter measurement. A D-band Low Noise Amplifier(LNA) die is designed by the modified transistor model. The simulation results show that the LNA obtains a gain more than 29 dB in 110 GHz-170 GHz range and the noise figure is lower than 6 dB. The results validate the proposed method.