The invention discloses high-fill high-heat-resistance polyvinyl alcohol-based microcellular foam type flame retardant paper.The microcellular foam type flame retardant paper is prepared through the steps that polyvinyl alcohol and a plasticizing foaming agent are mixed and swelled and then mixed with an inorganic flame retardant and a flame retardant synergist to obtain composite powder; the composite powder is added into a screw extruder for microcellular foam extrusion, cooling traction, flattening and winding are conducted.The vertical burning class is V-0, the limit oxygen index is 35%-41%, the tensile strength is 1.0-4.5 MPa, the apparent density is 0.05-0.50 g/cm<3>, the average cell diameter is 70-200 micrometers, and the thickness is 0.1-2.0 mm.The flame retardant paper is excellent in thermal resistance, can meet the requirement of rapid laser printing, is excellent in comprehensive performance and low in cost and can be prepared by directly adopting a thermoplastic processing method, the technology is simple and easy to operate, and continuous industrialized production can be achieved.