This article describes the development of a kind of full carbon-based humidity sensor fabricated on the paper substrate by handwriting. The electrodes were written by commercial pencils, and the sensitive layer was drawn with an oxidized multiwalled carbon nanotubes (o-MWCNTs) ink marker. The resultant devices exhibit good reproducibility and stability during the dynamic measurement. The response of the optimized paper-based sensor exhibits about five times higher than sensors fabricated on the ceramic substrate, which is owing to the hydrophilic property of the paper substrate. The structure of the sensitive layer formed by dispersing sensitive materials in the porous surface of paper substrates alleviates the inner stress in the process of bending. The response of printing paper-based sensors only shows the 6.7% decay even under an extremely high bending degree.