Abstract: In order to study the effect of homogenization treatment and test temperature on cracking susceptibility of Incoloy-800 alloys during tension, the alloy was treated by homogenization treatment, and then the high temperature tensile tests were carried out on Thermorestor-W thermal simulation test machine. The results show that the most sensitive test temperature range of the alloy cracking was 1 000℃ to 1 150℃. After homogenization treatment, the most sensitive temperature range was constant, but the threshold strain increased. After homogenization treatment the microstructure of the alloy changed obviously and the structure of grain boundary carbides changed from continuous lamellar to discontinuous granular, so that the tensile load and flow stress were decreased in the process of high temperature tension. Flow stress was the main factor to produce cracks during high temperature tension, the tendency of intergranular cracking and the crack sensitivity were enhanced when the flow stress exceeded intergranular binding force.