We developed a facile and reproducible method for fabrication of reduced graphene oxide (rGO) ultrathin films with high transparency (over 85% at 550 nm), uniform sheet resistances (~10 6 Ω/sq), and controlled thickness. The rGO ultrathin films can be successfully obtained when spray-coated rGO on glass slide was immersed in deionized water, and can be easily transferred to any substrates of interesting for further construction of optoelectronic-devices.