Hot subdwarf stars are important objects in the study of stellar evolution, binary evolution, Galactic structure, the UV-upturn phenomenon in elliptical galaxies, asteroseismology, model stellar atmospheres, surveys, etc. A series of meetings on hot subdwarfs have been held, the 1st in Keele, UK in 2003, the 2nd in Santa Cruz de La Palma, Spain in 2005, the 3rd in Bamberg, Germany in 2007. The 4th meeting will be in Shanghai, China, reporting and discussing the recent discoveries and developments in both theory and observation on hot subdwarfs and related objects. Note also that the regions around Shanghai are the best place to view the total solar eclipse on 22nd of July 2009, which will be the longest eclipse of the 21st Century being 6 minutes 38 seconds of its totality. An one day tour to view the eclipse will be arranged.