Abstract: Under the conditions of 160 ℃ and pressure of 1.2 MPa, the plant fibers core with different ratios were prepared with little fiberglass and plaster using rice shell powders and straw powders as raw materials, industrial water glass as binder. Then the plant fiber magnesium alloy sandwich panel was prepared through combining the core with the magnesium alloy plate, and the mechanical properties were studied. The results show that plant fiber magnesium alloy sandwich panel with light mass and high strength could be successful prepared at 120 ℃ and 1.2 MPa. The compression properties of the panel mainly depended on the core base material and solidification process, the additive had small effect. Adding proper fiberglass and plaster could increase the bending strength efficiently. The best bending properties could be obtained when the adding content of fiberglass and plaster respectively was 8wt% and 5wt%.