This study investigates the current construction of diaphragm plates inside the concrete filled tube (CFT) columns.  The types of hole on diaphragm plates and the material of the filled-in concrete were discussed.  The study object is the tower megacolumn, 272 m in height, of Nan Shan Plaza project in Taipei City, Taiwan.  Full size and one-fourth scale mockup tests were performed in three stages.  The test results show that the diaphragm plates with distributed small holes could reduce air bubbles underneath during the concrete pumping procedure.  The amount of air bubbles underneath the diaphragm plates would be reduced from about 10% to less than 2%.  The diameter of the distributed small holes should be greater than 8 cm.  The gross opening ratio of the small holes should be greater than the traditional design of one big hole in the center.  From the compression test results, the axial strength of the CFT columns using SCC with 0.04% expansion ratio and with either a big hole or distributed small holes on diaphragm plates, is not affected significantly.  The compressive strengths of these CFT columns  meet the design requirements.