Connections with exterior diaphragms are used widely in concrete filled steel tubular structures. The stress distribution regularity of ring plate has crucial influence to the right joint design as well as construction. Finite element simulation is applied to the two common types of connections with stiffener ring. The stress distribution regularity of ring plate a well as the development regularity of dangerous section are studied through changing loading methods and ring plate size . The main conclusions are achieved as follows: (1) The high stress plastic region of the 2 types will all not appear in the beam end, but inner the ring plate .This phenomenon will not be different as the changing of ring plate size. (2) The stress distribution of concentric arc ring plate is accord with the present test conclusions, which is to say, high stress regions are all in the corner of the boundary of beam and ring plate despite one way or two way loading. (3) The high stress region of side curved arc joint ring plate distribute in the 30 degree angle section of ring plate under one way loading, and between the 30 degree angle section of ring plate and the 45 degree inner ring plate under two way loading ,the ultimate stress in 45 degree region is a bit higher than 30 degree ,but penetrated plastic region was formed in the 30 degree section ,which indicates that the dangerous section is still in the 30 degree section. (4)Different loading methods can only change the stress distribution of ring plate but can not change the dangerous section, and even have no influence to the ultimate ring plate stress.