I-beams are primarily categorized into ordinary I-beams, light I-beams, and wide flange I-beams. Based on the ratio of flange height to web height, they are further classified into wide, medium, and narrow wide flange I-beams. The former two types are produced in sizes ranging from No. 10 to No. 60, corresponding to heights of 10 cm to 60 cm. At the same height, light I-beams feature narrow flanges, thin webs, and a lighter weight. Wide flange I-beams, also known as H-beams, exhibit a cross-sectional characteristic where the two legs are parallel and there is no inclination on the inner side of the legs. They are classified as economical cross-sectional steel shapes and are rolled on a four-high universal mill, hence also referred to as "universal I-beams". Both ordinary and light I-beams have established national standards.

The specifications of I-beams are expressed in centimeters of waist width. For example, an I-beam of size 10 has a waist width of 10cm. There are three types of I-beams: hot-rolled ordinary I-beams, light I-beams, and wide parallel-leg I-beams (H-beams). In China, the waist width of hot-rolled ordinary I-beams ranges from 100mm to 630mm, denoted as No.10 to No.63, with an inner leg wall slope of 1:6. The pass systems for rolling I-beams include straight pass system, skew pass system, and mixed pass system. Additionally, special rolling methods can be applied to I-beams.