Abstract All-cellulose composite films reinforced with ramie fibers were prepared from aqueous NaOH–urea solvent system via a simple pathway. The structure and physical properties of the modified ramie fibers and composite films were characterized by scanning electron microscope (SEM), wide angle X-ray diffraction (WAXD), Fourier transform infrared spectrometer, ultraviolet–visible spectroscope, thermogravimetry, biodegradation tests and tensile tests. The results revealed that a good compatibility existed between the modified ramie fibers and cellulose matrix. The all-cellulose composite films exhibited high tensile strength, good optical transmittance, thermal stability, and biodegradability. The tensile strength and elastic modulus of the composite films increased with an increase of the ramie fibers. These high-strength biodegradable films prepared by a “green” pathway have potential applications as packaging materials and biomaterials.