As the first biological material dedicated SAXS beamline, the electrons of BL19U2 beamline come from undulator which could provide high brilliance for BL19U2 end-stations. A double flat silicon crystal (111) monochromator is used in BL19U2 with a tunable monochromatic photon energy ranging from 7 to 15 keV. The RMS source size is 380 μm (H) x 25 μm (V) and divergence 80 μrad (H) x 30 μrad (V). The focusing element of the beamline is composed of two mirrors. One is the horizontal focusing mirror situated at 31.2 m from the source. The other one is the vertical focusing mirror situated downstream at 34 m from the source. Typically, the beam is focused to 0.33 mm (H) x 0.05mm (V) in the detector plane (22 m from the second focusing mirror), being 0.45 mm (H) x 0.11 mm (V) at the sample position (19.85 m from the second focusing mirror). The beam size in the sample plane can be further reduced at the expense of the photon flux.SAXS data is collected using a Pilatus 1M detector with over one million pixels.                                                                                           A homemade automatic solution-sample-changing peristaltic device has been developed for standard BioSAXS measurements at BL19U2. Samples and buffers with a volume about 60ul are injected and undergo continuous flow during experiments to eliminate radiation damage induced by the intense X-ray beam.The efficiency of standard BioSAXS measurements is also improved by realization of automatic sample-changing and cleaning about this device.                                                                                           Inline HPLC-SAXS measurement mode is now available at BL19U2 for the analysis of polydisperse macromolecules which are difficult to analyze using standard BioSAXS measurement device. Biological samples elute from the analytical size exclusion columns (including Superdex 200 Increase 10/300, Superdex 75 Increase 10/300 columns from GE Healthcare and WTC-015S5,WTC-050S5 columns from Wyatt) which are attached to Agilent 1260 Infinity HPLC system, then go through Agilent UV and Wyatt MALS/DLS detectors(DAWN HELEOS II and DynaPro NanoStar) and finally flow into an in-beam quartz capillary for SAXS measurement. The HPLC-UV-MALS/DLS-SAXS mode can significantly improve the monodispersity of samples and provide information on possible oligomeric states.                  Commercial Linkam HFSX350-CAP heating/freezing stage (-196℃ to 350℃) is available for in situ BioSAXS analysis.                                                                                    Commercial Biologic SFM-2000 stopped-flow device is provided for users to perform time-resolved BioSAXS studies triggered by rapid solution mixing.Sufficient scattered photons can be collected in 30-100ms.Up to several millilitres of sample should be prepared due to the dead volume of the device and repeated measurements.