Small steel hatch cover refers to the hatch cover with a small opening size and can be easily opened and closed with manpower. There are two main types of commonly used small hatchcovers, one is weathertight hatch covers, which are usually installed on each layer of open decks above freeboard decks and semi-closed superstructures or decks in the interior part of the deck; the other is a non-weathertight hatchcover, which can only be used on decks or platforms inside the ship. In addition, according to its shape can be divided into square, rectangular, circular. According to its density, it can be divided into weathertight, non-weathertight. According to whether it is higher than the open surface after installation, it can be divided into protruding type and embedded type. This paper mainly introduces the D-type small steel hatch cover, which is the flush weathertight hatch cover.