The influence of non-metallic inclusions on quality and performance of steel depends on not only the quantity of inclusions,but also the type,shape,size,distribution,and deformation behavior. In this paper,ANSYS finite element analysis software is used to simulate the stress field of inclusions appearing in heavy rudder arm steel castings,the effects of inclusion type,shape,distribution,and various loading conditions were studied. The micromechanics of inclusions in such castings were also analyzed. Such research provides further clarification on reaction mechanism of inclusions under complex loading conditions. The influence of non-metallic inclusions on quality and performance of steel depends on not only the quantity of inclusions, but also the type, shape, size, distribution, and deformation behavior. In this paper, ANSYS finite element analysis software is used to simulate the stress field of inclusions appearing in heavy rudder arm steel castings, the effects of inclusion type, shape, distribution, and various loading conditions were studied. The micromechanics of inclusions in such castings were also analyzed. Such research provides further clarification on reaction mechanism of inclusions under complex loading conditions.