This paper presented a novel stable FDTD algorithm to analyze the crosstalk for coupled metallic single walled carbon nanotube (SWCNT) interconnect based system. This algorithm considers the effect of parameter variation such as: interconnect parasitics, ambient temperature, driver aspect ratios, supply voltages and load capacitance. It has been observed that, the proposed algorithm takes lesser central processing unit (CPU) runtime compared to the conventional FDTD and overcomes the stability problem found in the conventional FDTD and remains stable for all time. Further, we have analyzed the propagation delay of SWCNT interconnect based system for different interconnect parameters. Based on the parameters, minimum delay and crosstalk is obtained. Moreover, the obtained delay and crosstalk is compared with the industry standard HSPICE simulations to check the model accuracy. Additionally, the relative stability of the response obtained from proposed FDTD model is verified using Bode plot and Root locus, the margin of stabilities are noticed as: stability margin for gain is −50 dB and phase stability margin is 40°.