Abstract Thermal stable BaAl 2O 4 nanocrystallites with pure spinel structure was successfully prepared at 650°C using amorphous BaAl 2(DTPA) 1.6(H 2O) 3 as precursor. The crystallization temperature via this synthesis way was about 500°C lower than that via traditional methods, such as sol–gel synthesis and solid-state reactions. The precursor was synthesized by simple inorganic reaction and can be decomposed into BaAl 2O 4 species at the temperature below 500°C, which was proved by DTA-TGA and X-ray photoelectron spectroscopy. X-ray diffraction results illustrated that BaAl 2O 4 crystal phase can be formed at 650°C with crystal size less than 60 nm. Especially, the crystal size increased weakly with either promoting the calcination temperature or prolonging the sintering time, indicating the high thermal stability of this material. The grain size was approximately 60 nm and the surface area was 10.88 m 2/g.