InAsSb epilayers with a cutoff wavelength of 4.8 μm have been successfully grown on InAs substrates by one-step liquid phase epitaxy (LPE) technology. The epilayers were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) transmittance measurements and scanning electron microscopy (SEM). The influence of different growth conditions on the optical and structural properties of the materi-als was studied. The results revealed that the good crystalline quality, mirror smooth surface and flat interface of InAsSb epilayers were achieved. They benefited from optimized growth conditions, i.e., sufficient homogeneity of the growth melt and a very slow cooling rate.