The experiment developed a novel method of microlens array preparation on polymethyl methacrylate (PMMA), which can fabricate the microlens with smooth surface, and the radius of curvature and size of lens could be controled by changing laser machining parameters. Laser irradiation induced glass evaporation and vaporization, so the liquid glass surface tranformed to sphere shape with the effect of surface tension. A microlens formed after the surrounded liquid glass cooling down. The lens radius of curvature could be minished with the laser output enhanced. But when the PMMA was impure or dirty, the microlens were bad with airballes and failure points.