The invention provides a cured composite material and a sand-fixing method for plant greening, a functional water soluble polyurethane composite cured material is prepared by composite reaction of a water soluble polyurethane resin chemical cured material (W-OH) and an ultraviolet degradation control agent, thereby greatly improving ultraviolet degradation resistance capability of the composite cured material, and degradation period of the composite cured material can be controlled. The ultraviolet degradation control agent comprises benzotriazole, benzophenone ultraviolet ray absorbent, and hindered amine and hindered phenol ultraviolet ray stabilizer. The cured composite material is sprayed to a sand surface with a spread plant greening composition, and a porous structured bonding layer is quickly formed on the desert surface, the bonding layer is advantaged by better air permeability, water conservation, and fertilizer-keeping characteristics, suitability for plant growth, realization of controlling more than 30 years of degradation period, and gradual realization of ecological environment remediation during sand-fixing.
