The BL19U1 protein complex crystallorgraphy beamline has the advantages of high luminous flux and low beam divergence. The U20 unshaker is used as the beamline light source with the working energy of 7-15KeV, covering the conventional heavy atom absorption edge, and has high flux and brightness near the commonly used energy of 12keV. Diffraction experiments using X-ray beams with good collimation can reduce the diffraction point broadening caused by the incompleteness of protein crystals, significantly improve the signal-to-noise ratio of diffraction experimental data, and thus improve the resolution of structure determination, especially for the crystals of biomacromolecular complexes. The beam divergence Angle of BL19U1 can reach to 0.1 mrad, which can determine not only the crystal structure of conventional proteins, but also the structure of macromolecular complexes with large cell size. The available experimental methods for crystal structure determination include multi-wavelength anomalous scattering (MAD), single-wavelength anomalous scattering (SAD), molecular replacement (MR), isomorphous replacement (MIR), etc.