PMMA(Polymethylmethacrylate) is a widely used transparent plastic material. During production process, leftover pieces of PMMA are often generated. For increasing the economic benefit of the PMMA industry, this technology can decompose PMMA leftovers into MMA monomer by pyrolysis process. Furthermore, high purity r-MMA can be obtained by distillation. The r-MMA consists with the specification which can recycle back into manufacture process.