High-strain-rate superplasticity and low-temperature superplasticity are favorable for making the use of superplastic forming for engineering ceramics even more wide spread. In this study, a silicon nitride based nanocomposite was developed for the purpose of improving the superplasticity. An amorphous powder was prepared by mechanical alloying of silicon nitride and metal titanium. A Si3N4-Si2N2O-TiN nanocomposite was fabricated by hot isostatically pressing the amorphous powder compact. A compression test was performed in the temperature range of 1573 K to 1873 K. The nanocomposite could be deformed at a strain rate of 10-2s-1, which was more than 100 times faster than that available for conventional superplastic Si3N4 at 1873 K. Furthermore, the nanocomposite was superplastically deformed in compression at low temperatures from 1573 K to 1673 K. The stress exponent and the activation energy of the nanocomposite were close to those of submicron-silicon nitride.