The fiber density per cross section of the Bamboo Guadua Angustifolia Kunth (GAK) was calculated by digital images processing. Three processes were done in the development of this work: preparation of the samples, digital pre-processing of the images acquired, and digital processing of the images acquired. For the preparation of the samples, the polishing with different abrasive papers and wool were done, and afterwards, it was added revealing ink on surface to make better the contrast between the fiber zones. The digital pre-processing of the images was based on the acquisition of sequences of images, doing a sweeping of the samples using an automatic plate. The digital processing consisted in the generation of panoramas with sequences of images acquired from the sample. The cross section fiber density was obtained by the calculus of the reason between digital measurement of the total area of the fibers and the total area of the sample. Finally, the values obtained for the fiber density were: 0.34, 0.41 and 0.43 for bottom, middle and top part of the culm respectively.