A microlens array with optical axis pa rallel to the substrate has been designed and implemented using polydimethylsiloxane (PDMS) soft lithography proc ess.At first,the deformation and the force-bearing of the thin PDMS membranes in microlens forming process a re analyzed.The finite element method is carried out to investigate the deformation of thin membranes with di fferent thicknesses and different pressures,and the reasonable microlens chamber structure is established.Then a microlens chamber is fabricated on an SU-8negative mold,and the chamber is sealed to a cover plate by using bonding technique.The curable polymers are injected into the lens chamber and cured while pressure is applied to keep the PDMS membranes deformed and generate a microlens array.Finally,the focusing effect of the microlens is tested by a homemade device.Results show that this method is simple,economically feasible,with controllable focal le ngth,and makes it particularly easy for integration with other micro systems,which may open up new possibilities for med ical detections and communications.