Abstract: The cosmic ray increases due to considerable depressions of cosmic ray cut off rigidity during large geomagnetic storms are investigated.Data from 11 superneutron monitors in world network are analyzed for six geomagnetic storms of various type during 1984-1989.The results show that the storm-time increases are due to existence of westward equatorial ring currents developing or intensifying during geomagnetic storms.The stronger the geomagnetic storm,the larger the storm-time increase.The storm-time increases have obvious latitude effect or geomagnetic cut off rigidity dependence.Beijing station is at the obvious region for the storm-time increase,and storm-time increases are of local tune dependence.This enhancement is larger at the daytime than at the nighttime.Showing that the intensifying ring current is asymmetrical.