The novel chitosan-based schiff bases DMABA-CSn were synthesized by the concentration reaction of narrow molecular distribution,low molecular weight chitosan CSn (n represents the degree of polymerization of chitosan, n=6, 8, 11) and 4-Dimethylaminobenzaldehyde (DMABA). The binding reaction between DMABA-CSn and bovine serum albumin (BSA) was studied with fluorescence spectroscopy, synchronous fluorescence spectropy, circular dichroism (CD) and isothermal tiration calorimetric (ITC). The fluoresonance quenching mechanism between DMABA-CSn and BSA was studied with fluorescence spectroscopy. The results indicated that DMABA-CSn (n=6, 8, 11) had the ability to quench the fluorescence from BSA and the quenching mechanism was a static quenching process with complex formation of DMABA-CSn/BSA. The effect of DMABA-CSn on the conformation of BSA was studied with synchronous fluorescence spectroscopy. The results suggested that the conformation of BSA was changed in the microenvironment of DMABA-CSn. Based on the thermodynamic results, the type of binding force was determined between DMABA-CSn and BSA. In addition, the thermodynamics results (ΔH<0, ΔS<0, ΔG<0) with ITC determination indicated that the binding process between DMABA-CSn and BSA was exothermic and spontaneous. What’s more, the main binding force was hydrogen bond and hydrophobic interaction. At the same time, with the increase of polymerization degree of CSn in a certain range of molecular weight, DMABA-CSn can be more easiliy combined with BSA. The research results have provided theoretical reference for the study on pharmacological mechanism of DMABA-CSn (n=6, 8, 11) as potential drugs.