Stress field is one of the primary factors influencing crack growth in rock. Pores significantly affect the distribution features of stress fields in porous rock. Based on the numerical reconstruction of the porous sandstone, we simulate the crack growth in porous sandstone subjected to splitting loads. The influences of the pores on the stress field during crack growth are analyzed. The distribution features of the stress σy and the evolution of the principal stress σ1 are disclosed in porous rock. The effects of the stress distribution on the crack growth behavior are discussed. It is shown that during crack growth the maximum value of the principal stress σ1 gradually increases for all of the porous models. The maximum values of tensile stress of σy decrease linearly with porosity increasing. This study presents a way to understand and characterize the distribution features of the stress field and the influences on the crack growth in porous rock.