Geochemical characteristics of radon and helium and their applications in seismology are systematically reviewed. Based on the factors affecting the concentrations of subsurface gases such as radon and helium in the crust, the annual (or diurnal) variations of the concentrations of subsurface gases are concluded, and comprehensively affected by many factors such as their geochemical characteristics, climate conditions, geological tectonics and regional tress fields etc. Advances of theory and experiment studies and formation of helium and radonanomalies in the past 30 years are summarized in detail. Finally, some suggestions on the further study of helium and radon and their applications in seismology are proposed in this paper. The following aspects would be further studied:(1) the relationship between migration mechanism of deep gases and seismology, (2) multiple monitoring of seismic measurements including radon, helium, carbon dioxide, mercury, methane, fluid, geothermics etc, (3) the selection of seismological station sites for subsurface gases observation, (4) the study on experiments of generating subsurface gas anomalies, (5) the processing methods of observation data etc.