Abstract: Stringent quality control is required necessarily in each step of casting process of aeroengine hollow turbine blade, where an evaluation on residual cores is also an indispensable link. Based on the immersion method, the structure characteristics and neutron detection ability of residual cores in hollow turbine blades were studied in this paper. The results show that residual cores with thickness of 0.2 mm and marked by Gd element can be clearly distinguished for cold neutron radiography. This high-sensitivity detection characteristic depends on the content of Gd element absorbed by residual cores, which is closely related to the porosity of residual cores, the accessibility of immersion solution and the complexity of inner cavity. The single-sided film shows the best image quality that is favorable to the accuracy of quantitative evaluation on residual cores. The immersion method does have some reliability problems, whereas it is suitable for neutron photography of porous residual cores after leaching.