In response to the failure problem of automobile engine connecting rods caused by insufficient material properties, for non-quenched and tempered steel C70S6, stress simulation and failure analysis of automobile engine connecting rods were conducted. Firstly, the macroscopic and microscopic structures of the fractured connecting rods were observed, and their mechanical properties were tested. Subsequently, the equivalent stress，equivalent strain and equivalent elastic deformation of the connecting rods were simulated by software ANSYS Workbench, and the stress concentration area was determined by establishing a three-dimensional model and setting reasonable boundary conditions and loads. The results show that the connecting rod exhibits ductile fracture characteristics, mainly due to the high hardness and insufficient toughness of the material, and the maximum stress and strain are concentrated in the part of the small head away from the rod body of connecting rod. By optimizing material properties and structural design, the reliability and service life of the connecting rods is effectively improved, providing a theoretical basis and practical guidance for the improvement of key components for automotive engines.