The manufacture, launching and placing of ultra-large perforated caissons are great challenges for the construction equipment and technique. Taking caissons of berth No.4 on the north pier of Dongjiakou area Qingdao port as an example, this paper presents the perforation plugging technique of suspended steel formwork, which recovers the shortage of conventional plugging methods. With this new technique, perforations on the midfeathers could be left unplugged and caissons can be placed at high tide. Moreover, the paper introduces the calculation and key construction technique in the launching and placing process of perforated caissons. The successful practice of the project provides a reference for the launching and placing process of ultra-large perforated caissons.