In this paper, a novel transparent thin film based on carbon nanotube (CNT) technology for radio frequency (RF) electromagnetic shielding is presented. The thin film, which is assumed to be infinite in length and width and tens to hundreds nanometers in thickness, consists of two layers of CNTs perpendicular to each other with a distance of hundreds of nanometers and a host medium which encloses the CNTs. The shielding effectiveness (SE) and optical transmittance of the thin film under normally incident plane-wave is both simulated by CST, a 3-dimentional full wave electromagnetic simulation software and theoretically calculated. Results from the theory and simulation fit well. The SE is still higher than 80 dB when the frequency rises up to 10GHz and the optical transmittance is higher than 80% from 300 nm to 1000 nm. Besides that, comparisons with metallic screens or multi-layered thin films are provided to demonstrate the superity of the proposed design.