The present invention relates to a method of preparing an insoluble separation matrix, which method comprises salt-treatment of a polysaccharide gel followed by cross-linking of the polysaccharide polymers. In one embodiment, the method comprises providing an aqueous solution of a gelatable native polysaccharide; lowering the temperature of the polysaccharide solution to a value below its gelling point; salt-treatment by adding at least one salt to the resulting polysaccharide; and cross-linking the salt-treated polysaccharide. The polysaccharide may be prepared e.g. into particles, membranes or monoliths.