Drill rod is a steel pipe with a thread at the end used to connect the surface equipment of the drilling rig and the drilling and grinding equipment or bottom hole device at the bottom of the well. The purpose of the drill pipe is to transport the drilling mud to the drill bit and together with the drill bit raise, lower or rotate the bottom hole device. Drill pipe must be able to withstand enormous internal and external pressure, twisting, bending and vibration. In the process of oil and gas extraction and refining, drill pipe can be used many times. Drill pipe is divided into three categories: kelly, drill pipe and weighted drill pipe. The connection sequence is kelly (1 piece) + drill pipe (n piece, determined by well depth) + weighted drill pipe (n piece, determined by drilling tool assembly design). The classification of drill pipes, drill pipe joints, drill pipe specifications, and the steel grade and strength of drill pipes are introduced in detail.