This invention discloses a method for treating sand or sandy soil in desert or desertified land, comprising spreading water and a solid organic substance in any order or by directly spreading an adhesive and cohesive solution containing the solid organic substance onto the surface of desert or desertified land, and then stirring the solution containing the solid organic substance or mixing water and the solid organic substance with sand on the surface of desert or desertified land in a uniform way by a stirring device to finally form a modified sand material. This sand treatment method can be directly implemented on the surface of desert or desertified land without transporting and discharging the mixture onto the surface of desert or desertified land, and thus saving cost and time.