In this letter, a technique to extract 2-port <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$S$</tex></formula> -parameters of an arbitrary vertically aligned carbon nanotube (CNT) array is proposed based on the multiconductor transmission line (MTL) model. A closed-form analytical solution has been developed to model multiwall CNT (MWCNT) arrays under a common mode excitation. Simulated <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$S$</tex></formula> -parameters from the MTL model are compared to those from the effective single-conductor (ESC) model. The absorptions of CNT arrays are calculated, and a good matching with measurement results has been obtained. Finally, some key parameters of CNT arrays such as wave propagation velocities for different dimensions and array sizes are investigated numerically.