Abstract: In order to achieve the target of long-focal length miniaturized near-infrared (NIR) system ,the telephoto optical structure was adopted to compress the axial dimension, and the telephoto ratio reached 0.53.Furthermore,the stray light was eliminated by properly setting the stop, and by choosing appropriate mechanical and optical materials,the athermal design was realized.In working temperature（40 ℃～+65 ℃），the image surface drift is smaller than focal depth, the modulation transfer function(MTF) 0.7 at 20 lp/mm,the spot is 4.7 m which is smaller than CCD pixel of 6 m, and the optical axis stability is 0.04 mrad.The system can gain good imaging quality and optical axis stability in worsened environment without focusing.Test result shows both the detection and recognition distances meet the requirements.