The applications of AMLA (aspheric micro lens array) have been frequently required in opto-electro industries, such as optical communication, contact image sensor (CIS) module of scanner, wafer level optics, etc. In addition to the typical requirements of aspheric lens, for instance form accuracy and surface roughness, the pitch error of each micro lens has been highly required. Three ultra-precision freeform machining methods have been widely applied for the manufacturing of AMLA, namely fast tool servo, slow tool servo and diamond milling. UPDM (Ultra-precision diamond milling) have the advantage with no tool interference problem in comparison with tool servo machining techniques. In this paper, the tool setting error compensation method and the tool path of UPDM has been developed for the fabrication of a 5 by 5 AMLA model. The form accuracy and surface roughness of each lenses of the AMLA was less than 0.2μm and 5nm, respectively. And the pitch error of each micro lens was less than 2μm in 25 micro lenses.