To improve the efficiency of optical coupling and the signal-to-noise ratio of long wavelength quantum well infrared detector(LW-QWIP), we designed and fabricated a quantum well subwavelength micropillar arrays structure targeting at 8.7 μm central wavelength. Different from the reported metal or dielectric microcavity structures, each pillar contains 50 periods of quantum wells and barriers, which combined with the filling factor lower than 0.18 is expected to considerably suppress the dark current while enhancing the efficiency of light absorption. Infrared spectrum measurement discloses that the micropillar arrays reflect only 8% in the wavelength range of 8~9 μm. Our study offers a practical scheme for sensitive infrared detection at high operation temperature.