To explore the secondary moments on the columns and beams in steel braced frame arising from the reaction introduced by the gusset plates of bracing members with the developing story drift, and to obtain this unwanted effects on the frame members, a series of diagonally braced frames (one-story and one-span) where the braces are connected with gusset plates are simulated by using shell elements in ANSYS program. By considering two conditions in which the brace is compressed or tensioned respectively under story drift, the secondary moments in the columns and beams influenced by the key factors such as gusset plate thickness, length of gusset plate, axial compression ratio of columns, and yield strength of steel used in the frames are investigated. It is shown that the secondary moment increases with the increase of story drift, and can even form plastic hinges in both the beam and the column if a stronger gusset plate is employed. At elastic limit state of the braced frames, the tensioned brace can cause smaller secondary moment than the compressed one. The axial compression ratio of columns can slightly decrease the secondary moment. Based on the statistic results of the parameter analysis, reasonable values of the secondary moments are suggested for the engineering design of the columns and beams.