The aim of this study is to investigate the potential as a novel biomaterial of low molecular water soluble chitosan and its derivatives. The ability of the gene condensation was investigated by gelretardation assay. LMWSC itself with free-amine group was formed at the low weight ratio, above a 1:2 weight ratio of plasmid DNA : LMWSC. LCP and LCP-Ch were accomplished the complex formation above 1:8 and 1:24 as modify with PEG and cholesterol on the amine-group, respectively. The particle size of complexes was different according to the pH of media. Particle sizes at the pH 6.5 and 7.0 were about 100~120 nm and 120~160 nm, respectively. Because LMWSC at the pH 6.5 has the strong positive charge, it can be formed the compact complex with plasmid DNA. Also, the surface charge of complex was depending on the pH. At the pH 6.5, the surface charge of complex was higher than that of pH 7.0. The zeta potential of LCP modified with PEG or LCP-Ch modified with cholesterol has lower positive value than that of LMWSC itself due to the decrease of the positive charge.