Gravitational collapse signature is essential to understand how star formation but it is very difficult to obtain observational evidence for high mass star formation.Recent development in technology has boosted the search of inflow motion.A number of high-mass collapse candidates were obtained with single dish observations,mostly shown in "blue profile".Physical parameters and correlations between inflow velocity and source masses were obtained and analyzed.The infalling signatures seem more common in regions with developed radiation than in younger cores,which opposes the theoretical prediction and is also very different from that of low-mass star formation.Interferometer studies so far confirm such tendency with more obvious "blue profile" or inverse P Cygni profile.Results seem to support high mass stars form via accretion-outflow-disk.Further investigation is needed to examine weather infall is monolithic or competitive.