In this study, poly(methyl methacrylate)( PMMA) microlens array for a back light unit(BLU) application was fabricated by an inkjet printer, which loaded piezoelectric microchannel mounted 30 mm nozzles to deposit polymer droplets via drop-on-demand fashion. Before the inkjet printing, the surface of PMMA substrates was modified chemically by a phase separation technique. The surface topologies and aspect ratios of microlens were measured. A 5.2 x 7 cm(2) BLU plate with microlens arrays printed by the inkjet method was fabricated for the application of a mobile phone.