The common material of the shaft is high quality carbon structural steel, such as 35 steel, 45 steel and 50 steel, of which 45 steel is the most commonly used. Common carbon structural steels such as Q235 and Q275 can be used for less important shafts with smaller loads, larger stresses and limited shaft sizes. Alloy structural steels may be used, while tempered steels are usually used for heavy duty shafts. After quenching and tempering, the obtained sostenite structure has better comprehensive mechanical properties, higher strength, higher impact toughness, lower brittle transition temperature and higher fatigue strength than the mixed ferrite structure obtained by normalizing or annealing. Quenched and tempered steel includes 35 steel, 45 steel, 40Cr, 45Mn2, 40MnB, 35CrMo, 30CrMnSi, 40CrNiMo, etc. Chrome-nickel steel can be used for cross section of very important shafts. Heat resistant steel or stainless steel may be used for shafts under high temperature or corrosion conditions. At normal operating temperature, the elastic modulus of alloy structural steel is similar to that of carbon structural steel. It is not appropriate to select alloy structural steel to increase the stiffness of the shaft. In order to meet the performance requirements of spline shaft, we can choose bearing steel GCr15. GCr15 steel is a kind of high carbon chromium bearing steel with low alloy content, good performance and most extensive application. After quenching and tempering, high hardness, uniform, good wear resistance, high contact fatigue performance.