The hot forging die is subjected to the combined action of alternating thermal stress and mechanical stress during the working process, and  it is prone to failure due to wear, cracking and plastic deformation.Aiming at the problem of low service life of hot forging die for a certain type of sliding fork, the main causes of failure were analyzed according to its failure modes. It is found that the failure position of final forging die is mainly on the end face of punching boss, the hot crack is radial, and the punching boss has a certain degree of plastic bending.Theoretical analysis and numerical simulation results show that the long-term contact of the end face of the punching punch with the hot blank leads to an increase in temperature and a decrease in strength and stiffness. Under the combined action of thermal stress and contact stress for a long time, the end face cracks and bends to a certain extent. By controlling the upsetting amount of blank, improving the rigidity of boss, optimizing the height of punching boss, the rationality of material flow,and using the 3D printing technology and the material with high hot hardness to manufacture the punching boss, the die life is significantly improved.