The characteristics and the reason of its formation of casting defects in different areas of directional solidified turbine blades of DZ22B nickel base superalloy were investigated by means of SEM and EDS. The results show that the crack defects are mainly distributed in the middle and upper parts of the blade body

and its formation mechanism is mainly due to the excessive eutectic structure of the blade during the solidification process. While the loose defects are distributed in the blade body and the edge plate

and are generated in the dendrite near the eutectic structure. The small gap between dendrites and insufficient filling and the CO gas generated by the reaction not released in time are the two main reasons for the formation of looseness.