Refractive square based arch GaAs microlenses array was fabricated by a novel method, i.e., the curvature compensation method. The new method was proposed to increase the focal length of refractive microlenses array . Scanning electron microscopes (SEM) show that microlenses are square based arch arrays, and surface , stylus measurement shows that the focal length of the microlenses array is 3861.70μm,which is much longer than 200μm and it is the longest focal length of the microlenses array of the same size fabricated by conventional methods including photolithography, melting and ion beam milling. The microlenses array (MLA) device and infrared focal plane array (IRFPA) device were aligned under an IR microscope and coupled with a kind of infrared glue. The IR response characteristics of the hybrid device were improved greatly.