In this work, experiments to produce a series of nanocomposites based on natural chitosan and nano-clay (MMT) were conducted. Commercially available montmorillonite (MMT) was used as a nanofiller. CS-MMT nanocomposites were prepared using the casting method. Thin nanocomposite foils were neutralized in NaOH solution, then the nanocomposite foils were soaked in simulated body fluid (SBF). Kinetics of crystallization of the apatite structure was observed using PIXE, FTIR-ATR and SEM/EDS techniques. It was shown that high concentrations of calcium and phosphate ions were located inside the nanocomposite structure. Bioactivity phenomena was initiated first in the nanocomposite foils (CS/MMT) and then in pure chitosan foils. These results suggest that the nano-clay particles (MMT) distributed in the biopolymer matrix acted as nucleaction centers of apatite. An apatite layer on pure chitosan crystallized much more slowly than in the case of nanocomposite materials. The CS-MMT nanocomposites therefore seem to be promising materials for bone repair implants because of their inherent bioactivity.