The orthogonal design had been employed to study the reaction conditions of chitosan(CTS) condensing with benzaldehyde. The optimum reaction conditions were as follows: chitosan swelling in 3% HAc 30 min, n(chitosan)/n(benzaldehyde)=1:6, pH=5.0, reaction time was 4h at 70℃,the yield of resin could reached 86.73%.