Abstract: With the rise of virtual reality and somatosensory games, the human posture estimation has received increasing attention. The Fresnel optical microstructure lens in the human posture estimation sensing system based on pyroelectric infrared sensor was designed. After analyzing the theoretical formula of the cone even aspheric surface, the aspheric surface coefficients at all levels were calculated. Through simulation analysis, when the polymethyl methacrylate (PMMA) is selected as the material and the LHI968 detector with six sensitive element area of 2×1 mm² as well as field angle of 100°×100° is adopted as the detector, the overall dimensions of the Fresnel lens is 28 mm×32 mm, the curvature radius of the front and back surface are 43.7 mm and 45.2 mm, respectively, and the center thickness is 0.6 mm. The final simulation results show that the light energy utilization rate of each detector is 96.70%, 94.8%, 96.95%, 97.75%, 90.65% and 90.15%, which can satisfy the response of the infrared light to different parts of the human body, so as to achieve the accurate estimation of the human posture.