Abstract: Based on cellulose nanofiber (CNF) and graphene oxide (GO) co-stabilized Pickering emulsion with dichloroethane solution of poly (methyl methacrylate) (PMMA) as the oil phase, the cellulose nanofiber-reduced graphene oxide/poly (methyl methacrylate) (CNF-rGO/PMMA) electromagnetic interference (EMI) shielding composites were subsequently prepared by filtration, reduction and hot-pressing method. The mass fraction of GO in the EMI shielding composites was adjusted by the polymer concentration in the oil phase and the volume ratio of water to oil phase. The effects of GO reduction method, the mass fraction of GO and hot-pressing process on the morphology, structure and property of the obtained CNF-rGO/PMMA EMI shielding composite were studied. The reduction of hydrazine hydrate can transfer GO to rGO more effectively. The hot-pressing process facilitated CNF-rGO sheets surrounding PMMA micro-particles to closely be compacted with PMMA and meanwhile to form a 3D network structure of CNF-rGO sheets which endowed an excellent electrical conductivity of the obtained CNF-rGO/PMMA EMI shielding composites. The CNF-rGO/PMMA EMI shielding composites have good EMI shielding effectiveness and stability in the range of 8.2-12.4 GHz with over 20 dB of EMI shielding effectiveness and possess application in civil EMI material.