Recent studies show that a through beam connections composed of concrete filled square steel tubular column and steel beam have been identified as an ideal rigid connection. In this paper a 3-D nonlinear finite element models were conducted for CFSST column and steel beam connection under monotonic load using ABAQUS software. Each model includes a CFSST column and single steel beam passing through the column. The main scopes are to identify the modes of beam failure and joint shear failure. In addition the effect of an extra shear plate welded to beam web inside the column was investigated. This result can be used for designing of through beam connection.