Abstract: Dialdehyde chitosan (DCTS) was prepared by periodate oxidation. In terms of high oxidation degree and low weight average molecular weight, the conditions of DCTS preparation were optimized as follows. The deacetylation degree of CTS was 95.1%. The initial oxidation pH was 3.0. The mole ratio of sodium periodate to GlcN unit of CTS was 1.1. The oxidation duration was 6 h, and the temperature was 20-25 ℃. DCTS was then used as a crosslinker of collagen fiber. The effect of oxidation degree of DCTS on its crosslinking performance was investigated. DSC and mercury intrusion porosimetry analysis showed that the thermal denaturation temperature of collagen fiber rose with the increase of oxidation degree, and the porosity of collagen fiber was reduced accordingly. These results suggested that the crosslinking performance of DCTS was enhanced with the increased oxidation degree of DCTS.