In order to ensure the accuracy of internal dimension, core supports made of Pt are normally used in the complex hollow single crystal turbine blades. However, the influence of core supports on the microstructure and property of DD5 single crystal turbine blades has not been reported. In this paper, core supports made of Pt were inserted into DD5 thin-wall plate specimens to observe the effect of core support on the microstructure and element segregation. In addition, the typical properties of DD5 thin-wall plate specimens with core support made of Pt were tested to clarify the influence of core support on alloy properties. The results showed that core support made of Pt had great bonding with DD5 alloy without obvious heterogeneous interface. The core support made of Pt was completely alloyed, the microstructure of core support was consistent with DD5 alloy, no new phase was observed. Core support made of Pt had no influence on the microstructure of DD5 alloy, but the degree of element segregation of DD5 alloy was increased. Moreover, core support made of Pt had no negative effect on the tensile property at room temperature, tensile property at 870℃ as well as stress rupture property at 1093℃/158MPa of DD5 thin-wall plate specimens. The fracture mode of DD5 thin-wall plate specimens with core support was interdendritic rupture, and cracks initiated and propagated along the interface between carbide and matrix.