The invention relates to a high strength flame-retardant sound and heat insulation sandwich board and a preparation method thereof. The sandwich board comprises, from top to bottom, an outer panel, a non-woven fabric, an adhesive film, a rubber sound insulation felt, an adhesive film, a foam core material, an adhesive film, a rubber sound insulation felt, an adhesive film, a non-woven fabric and an outer panel in order. The preparation method consists of: weighing polypropylene resin, a flame retardant, an antioxidant, and an anti-aging agent, mixing them fully and evenly, then adding the mixture into an extruder to perform extrusion laminating and performing compounding with a continuous fiber, flattening the product into a unidirectional prepreg tape; cutting the prepreg tape, laying the cut prepreg tapes on a mould in a transversely and longitudinally staggered way, carrying out hot pressing and cold pressing to obtain a bi-directional continuous fiber reinforced polypropylene resin composite outer panel; putting one side of the outer panel with the non-woven fabric together, firstly conducting hot pressing and then performing cold pressing to obtain the outer panel of the composite non-woven fabric; and laying all layers of materials according to a product order, and carrying out cold pressing, thus obtaining the product. Compared with the prior art, the high strength flame-retardant sound and heat insulation sandwich board provided by the invention has high bending properties and shock resistance, etc.