Collagen-nanocellulose composites have been widely used in biomedicine and tissue engineering. However, the detailed mechanism underlying the effects of nanocellulose on the structure of collagen hasn’t been elucidated. As the main component of skin tissue, the conformational disturbance of collagen triggered by nanocellulose may shed light on the biocompatibility of nanocellulose. Therefore, molecular dynamics simulations were carried out to gain insights into the interactions between nanocellulose and collagen. Four different crystal planes of cellulose ((110), (100), (1-10), (010)) have been constructed and the adsorption of collagen onto the four faces has been investigated respectively. It has been found that the structure of collagen remained intact during the binding without chain separation. The intactness of collagen supported the point that the nanocellulose has good biocompatibility. The results derived from umbrella sampling showed that (110) and (1-10) faces exhibit the strongest affinity with collagen, which may be attributed to its hydrophilicity and rather flat surfaces. The hydrophobicity of (100) face and roughness of (010) face diminished the affinity with collagen. The occupancy of hydrogen bonds was low and hydrogen bonding interactions fail to make significant contributions to the binding of nanocellulose and collagen. These findings provided insights into the interactions between cellulose and collagen at an atomic level, which may guide the design and fabrication of collagennanocellulose composites. Furthermore, the biocompatibility of nanocellulose validated in the study may help promote the biological application of nanocellulose involved composites.