In this paper, the properties of chitosan nanoparticles and bovine serum albumin-loaded chitosan nanoparticles prepared with sodium tripolyphosphate at different pH values were discussed. Interactions in chitosan nanoparticles and bovine serum albumin-loaded chitosan nanoparticles were analyzed by Fourier transform infrared spectroscopy and differential scanning calorimetry. The results indicated that there were more complicated interactions in chitosan nanoparticles prepared at different pH values. When the pH values were lower or higher than isoelectric point value of target protein (bovine serum albumin), the big different interactions occurred in chitosan nanoparticles. These differences also would result in different releasing properties.