Abstract: Combined directional solidification experiments with ProCAST numerical simulation methods, the formation tendency of stray grain and porosity defects in circular platform areas under ＜001＞ orientation and a 15° deviation from ＜001＞orientation was investigated. The results show that the microstructure of the circular platform is divided into three main parts:the central area, the expansion area and the stray grain area. Among them, the stray grain area expands as the platform position raises and tends to form on the side opposite to the center of the casting group; in contrast, porosity defects mainly appear on the side opposite to the furnace wall. When the crystal orientation deviates from the ＜001＞ direction, it is observed that the formation tendency of stray grain defects on the platform increases slightly, but at the same time, it reduces the formation tendency of porosity defects. Finally, combing the temperature field evolution results from numerical simulation, the influence mechanism of crystal orientation on the formation of stray grain and porosity defects in the platform area is analyzed.