The invention relates to a composition for a flame-retardant polyvinyl chloride (PVC) plastic foam board, and the flame-retardant PVC plastic foam board produced by a double screw extrusion method. The composition comprises the following components in part by weight: 100 parts of polyvinyl chloride, 5 to 25 parts of polyacrylate copolymer, 0 to 30 parts of chlorinated polyethylene, 0 to 30 parts of chlorinated polyvinyl chloride, 20 to 70 parts of flame retardant and smoke suppression agent, and 0 to 5 part of plasticizer, and also comprises a resin melt reinforcing agent and additives such as a foaming agent, a lubricating agent and a stabilizing agent and the like. After the produced flame-retardant PVC plastic foam board is detected by Shanghai Building Material and Component Quality Surveillance Office and State Laboratory of Fire Science (University of Science and Technology of China, Hefei), the oxygen index is more than or equal to 32, the smoke density grade is less than or equal to 75, the average combustion time is less than or equal to 30 seconds, the heat release rate is less than 250W/g, the heat conductivity is 0.047W/m.K, and the flame-retardant PVC plastic foam board meets the B1 requirement of GB/T8624-1997, and meets the V-0 standard of UL-94.