Recently, electromagnetic (EM) shielding (EMS) window, especially the ultrathin, transparent EMS active layer, has been the primary objective of extensive studies because of its widely potential applications in stealth technology, high radiation pollution, and others. However, several defects, including opacity and large thickness, have severely restricted the application in optical EMS devices. Herein, we developed an ultrathin and highly transparent EMS active layer on a rigid glass and a flexible polyethylene terephthalate substrate by chemical doping CVD (chemical vapor deposition) graphene with nitric acid (HNO3) as the P-type dopant, which has a 91% transmittance and 1/1000 thickness compared to the conventional EMS active layer. The HNO3-treated graphene shows excellent EMS efficiency by a factor of 4.5, significantly compensating for the adverse effects of the grain boundaries between CVD graphene crystals. Additionally, 55% HNO3 is the most suitable for achieving high EMS effectiveness, which can be significantly improved by treating for only 5 min. This unique chemical-doping CVD graphene holds potential for being exploited as a transparent active layer in numerous EMS applications.