Subwavelength diameter microfiber with carbon nanotube (CNT) cladding attracts wide attention for its significant effect on evanescent coupling and interaction. In this paper, the physical mechanism and spatial expression of the light field near CNT coated microfiber are analyzed by the electromagnetic calculation and mode field analysis experiments. The simulated and experimental results demonstrate that light field distribution along the CNT coated microfiber shows the resonant modes with intensity attenuation locating at $\sim 0\mathrm{\mu m}$, 1.7 μm, 3.3 μm at the direction of core radius. The investigation about interaction between evanescent wave and CNT films will inspire the future application of CNT films and microfiber based lasers, all-optical switches, wavelength converters, sensors, and other integrated functional photonic devices.