Thread connection is one of the most common connection methods, which has been widely used in mold, aerospace, petrochemical, 5G communications, new energy vehicles and other industries. Tap is a special tool for small and medium-sized internal thread machining. It is almost the only effective process method for small thread hole machining. It is different from the traditional tools such as turning tools and milling cutters. It is closed for cutting and belongs to semi-closed and multi-cutting edge forming processing. Its quality directly affects the internal thread processing quality and processing efficiency. Starting from four common types of tap, the processing characteristics, processing materials and application scope of different taps are expounded and the geometric structures of taps are briefly introduced. Secondly, the common processing problems and failure forms of tap are introduced. Then, the effect of single surface treatment technology on the surface quality and processing performance of the tap is emphatically expounded, and the relationship between the surface treatment technology of the tap in China and abroad, including edge passivation, physical vapor deposition (PVD) nitride coating and special film and cutting performance is investigated. At the same time, the strengthening mechanism of different surface technologies is summarized, and the future prospect is put forward according to the research status in China and abroad.