Water soluble chitosan (WSC) removed salts in amine group of glucosamine unit has a strong positive charge and high reactivity. Therefore, WSC can be a superior gene carrier and easily modifying with functional group. In this study, we prepared various WSC derivatives with MPEG and cholesterol and performed the electrophoresis, transfection efficiency and cytotoxicity. First, WSC was formed compex with DNA above 1:8 weight ratio, but WSC derivatives was formed higher weight ratio than itself, above 1:16. It was considered that the positice charge of WSC derivatives were declined due to substitute with MPEG or cholesterol in amine group of glucosamine unit. In the transfection test, WSC 10K was showed higher transfection efficiency than WSC 18K, but its derivatives was a contrast to this result. In cytotoxicity test, all WSC and its derivatives complexes showed negligible cytotoxicity for 293T cells. Therefore, WSCs having free amine group will be useful in the development of safe gene carriers.