Expanded polystyrene boards are produced by mixing resin with polymer, injecting a catalyst during the heating process, and then extruding a continuous, closed-cell foam plastic board. These boards feature an independent, sealed bubble structure and are an environmentally friendly insulation material with excellent properties such as high compressive strength, low water absorption, moisture resistance, airtightness, lightweight, corrosion resistance, and ultra-anti-aging (virtually no aging with long-term use), as well as low thermal conductivity.