The present invention relates to a zinc oxide-cellulose nanocomposite made of cellulose and zinc oxide nanoparticles and to a preparation method thereof. The nanocomposite of the present invention is prepared by producing zinc oxide nanoparticles as seeds on the surface and/or inside of a cellulose film and growing the seeds into zinc oxide crystals to form a zinc oxide layer strongly attached to the cellulose film. The nanocomposite of the present invention has significantly improved piezoelectricity compared to simple cellulose piezoelectric paper and may be used for LEDs and photovoltaic power generation devices thanks to zinc oxide doped therein.