As a new group-IV semiconductor alloy, Ge1-xSnx is a very promising material for applications in photonic and microelectronic devices. In this work, high-quality germanium-tin (Ge1-xSnx) alloys are grown on Ge(001) substrates by molecular beam epitaxy, with x=1.5%, 2.4%, 2.8%, 5.3%, and 14%. The Ge1-xSnx alloys are characterized by high resolution X-ray diffraction (HR-XRD), Rutherford backscattering spectra (RBS), and transmission electron micrograph (TEM). For the samples with Sn composition x 5.3%, the Ge1-xSnx alloys each exhibit a very high crystalline quality. The ratio of channel yield to random yield (min) in the RBS spectrum is only about 5%, and the full width at half maximum (FWHM) of the Ge1-xSnx peak in HR-XRD curve is 100''. For the sample with x=14%, the crystalline quality of the alloy is degraded and FWHM is 264.6''.