In order to detect the geometric contour errors of small parts using machine vision inspection technology, a high definition double telecentric optical lens is designed. The optical parameters are setup according to the requirements of detection. The structure analysis method for overall structural design is applied to construct the initial optical structure. The optical software Zemax is used to optimize the initial optical structure. The aspherical design is introduced to this lens, which can not only simplify the structure, but also effectively balance the system aberration and greatly improve the image quality. This structure realizes design requirements of low distortion (maximum distortion is less than one pixel), high resolution[modulation transfer function (MTF) at Nyquist frequency of 90.91 lp/mm is greater than 0.7, MTF at full field of 400 lp/mm reaches 0.15] and double telecentric system.