The improvement of sensitivity for uncooled InAsSb photodetectors with the wavelength longer than 8μm is studied.InAsSb thick epilayers with long wave length were grown on InAs substrates by melt epitaxy (ME) technique.The thickness of t he epilayers reaches 50μm X-ray diffraction (XRD) spectra show that the epilayers are single crystals with high quality.Electron probe microanalysis (E PMA) composition distribution images exhibit that the distribution of Sb in the epi layers is fairly homogeneous.The photoconductors were fabricated using the materials,and Ge imm ersion lenses were set on the detectors.Under uncooled condition,the spectral photore sponses of the devices demonstrate that the detectivity of InAs 0.06Sb0.94 detectors is 1.3×10^9cm·Hz1/2·W－1 and 2.8×10^8cm·Hz1/2·W－1 at the wavelengths of 8μm and 9μm , respectively,which is improved by one order of magnitude compared with that of InAs0.02Sb0.98 detectors.This is due to the increasing of arsenic composition in InAs0.06Sb0.94 materials.The pe ak detectivities at the wavelength of 6.5μm of InAs0.06Sb0.94 and I nAs0.02Sb0.98 are higher than 1.0×10^9cm·Hz1/2·W－1,indicating the possibl e applications for infrared (IR) detection and imaging.