It provides a gene-entrapping liposome preparation which can be preserved over a long period of time, and a process for the preparation of the same. The preparation can be prepared by adding an aqueous solution of disaccharide to gene-entrapping liposomes. The frozen preparation can be preserved for 6 months or more at preservation temperature of −20° C., and the preparation shows excellent restoration ability in water and does not show reduction in biological activity. In the case of the lyophilized preparation, it can be preserved for longer time of about 1 year, shows excellent restoration ability in water, and does not show reduction in biological activity.