Ti2AlNb-alloy has attracted considerable attentions as a potential material to long-time service at 650–750°C in aerospace industry. In this paper, the bulging testing experimental setup was set up, which can test the formability of the thin-wall sheet at the temperature range 300 to 1000 °C. The forming limit curve (FLC) of the rolled sheet at 970°C with the equivalent strain rate 0.001s-1 was tested by gas bulging tests by adjusting the insert dies, with minor-major axis ratios 1/4, 2/4,3/4 and 1, and the un-bonded bi-layer bulging method. The gas bulging pressure was fine controlled by the D. Banabi’s formula. The mean equivalent strain rates are calculated, which was in the range of 0.00115~0.00196. The results show that the gas bulging testing was a nice method to test the accurate FLCs without the errors induced by temperature and friction, which can be directly used to predict the formability in hot gas forming with a constant equivalent strain rate.