Serials InAs x Sb 161 x samples grown on GaAs (0020021) substrates by solid source molecular beam epitaxy (MBE) have been investigated. The high-resolution X-ray diffraction (HRXRD) and atomic force microscope (AFM) results reveal that the quality and the surface morphology of InAs x Sb 161 x strongly depend on the III/V ratio, growth temperature and the thickness of nucleation layer. When growth temperature is 40002°C, In:As:Sb is about 1:0.4:2, and the thickness of the nucleation layer is 3002nm, the sample has the smallest FWHM (797 arcsec), much better than the recent results [S. Nakamura, P. Jayavel, T. Kyama, Y. Hayakawa, J. Crystal Growth 300 (2007) 497; F. Gao, N. Chen, L. Liu, X.W. Zhang, J. Wu, Z. Yin, J. Crystal Growth 304 (2007) 472]. These results demonstrate that much better samples can be obtained by MBE. AFM surface particle analysis results show that surface morphology strongly associates with the surface particle size. Small particle size makes surface smooth and large particle size makes surface rough. Through optimizing the growth conditions, our samples have better crystal quality and smoother surface morphology. The sample which has the best crystal quality shows that the carrier mobility and density is 1.3×10 4 02cm 2 /V02s and 1.3×10 17 02cm 3 at room temperature