In order to meet the imaging requirements of OLED defect monitoring, a linear scanning lens of high-resolution is designed. The optical system is designed on the basis of double Gauss optical structure, the focal length of the lens is 116 mm, the magnification is 0.5, the object side numerical aperture is 0.038 and the linear object field of view is120mm.The modulation transfer function (MTF) of the len can reach more than 0.2 at Nyquist frequency of 100lpmm which can be obtained by Zemax simulation, and the diffraction limit can be reached. All the field of view points are basically within the Airy patch, and the RMS radius is small. The symmetry characteristic of double gauss is used to reduce the distortion, and the relative distortion is less than 0.5%. According to imaging requirements for adjustable depth of field and exposure( that is the switching requirements of F# ) and structural arrangement of optical components, the opto-mechanical structure design with variable aperture diaphragmof lensis provide. Finally, the imaging quality of the lensis detected by MTF tester. The experimental results show that thelens can meet the industrial imaging needs of OLED screen defect detection function.