Galactosylated chitosan was conjugated with poly(vinyl pyrrolidone) (PVP) as a hydrophilic group. The complex formation of GC-graft-PVP (GCPVP)/DNA complexes was confirmed by agarose gel electrophoresis. The morphology of the complex observed by atomic force microscopy had a compact and spherical shape, around 40 nm particle sizes at a charge ratio of 3. The binding strength of GCPVP 10K/DNA complex measured by ethidium bromide binding assay was superior to that of the GCPVP 50K/DNA one, probably attributable to its higher flexibility due to the smaller size, whereas the DNase I protection of GCPVP 10K/DNA complex was inferior to that of the GCPVP 50K/DNA one. This indicated that effective complex formation required both higher binding strength and minimal molecular weight of polycation enough to induce the condensation of DNA. The DNA-binding property of GCPVP mainly depended on the molecular weight of chitosan and composition of PVP.